Authors:Rony Izhar; Frida Ben‐AmiPages: n/a - n/aAbstract: 1.Host age is one of the most striking differences among hosts within most populations, but there is very little data on how age‐dependent effects impact ecological and evolutionary dynamics of both the host and the parasite.
2.Here we examined the influence of host age (juveniles, young and old adults) at parasite exposure on host susceptibility, fecundity and survival as well as parasite transmission, using two clones of the water flea Daphnia magna and two clones of its bacterial parasite Pasteuria ramosa.
3.Younger D. magna were more susceptible to infection than older ones, regardless of host or parasite clone. Also, younger‐infected D. magna became castrated faster than older hosts, but host and parasite clone effects contributed to this trait as well. Furthermore, the early‐infected D. magna produced considerably more parasite transmission stages than late‐infected ones, while host age at exposure did not affect virulence as it is defined in models (host mortality).
4.When virulence is defined more broadly as the negative effects of infection on host fitness, by integrating the parasitic effects on host fecundity and mortality, then host age at exposure seems to slide along a negative relationship between host and parasite fitness. Thus, the virulence‐transmission trade‐off differs strongly among age classes, which in turn affects predictions of optimal virulence.
5.Age‐dependent effects on host susceptibility, virulence and parasite transmission could pose an important challenge for experimental and theoretical studies of infectious disease dynamics and disease ecology. Our results present a call for a more explicit stage‐structured theory for disease, which will incorporate age‐dependent epidemiological parameters.
This article is protected by copyright. All rights reserved.PubDate: 2015-02-09T00:56:28.845454-05:DOI: 10.1111/1365-2656.12352

Authors:Sarah L. Amundrud; Diane S. Srivastava, Mary I. O'ConnorPages: n/a - n/aAbstract: 1.Herbivore communities can be sensitive to changes in predator pressure (top‐down effects) and resource availability (bottom‐up effects) in a wide range of systems. However, it remains unclear whether such top‐down and bottom‐up effects reflect direct impacts of predators and/or resources on herbivores, or are indirect, reflecting altered interactions amongst herbivore species.
2.We quantified direct and indirect effects of bottom‐up and top‐down processes on an eelgrass (Zostera marina) herbivore assemblage. In a field experiment, we factorially manipulated water column nutrients (with Osmocote™ slow‐release fertilizer) and predation pressure (with predator‐exclusion cages) and measured the effects on herbivore abundance, richness, and beta diversity. We examined likely mechanisms of community responses by statistically exploring the response of individual herbivore species to trophic manipulations.
3.Predators increased herbivore richness and total abundance, in both cases through indirect shifts in community composition. Increases in richness occurred through predator suppression of common gammarid amphipod species (Monocorophium acherusicum and Photis brevipes), permitting the inclusion of rarer gammarid species (Aoroides columbiae and Pontogeneia rostrata). Increased total herbivore abundance reflected increased abundance of a caprellid amphipod species (Caprella sp.), concurrent with declines in the abundance of other common species. Furthermore, predators decreased beta diversity by decreasing variability in Caprella sp. abundance among habitat patches.
4.Osmocote™ fertilization increased nutrient concentrations locally, but nutrients dissipated to background levels within 3 m of the fertilizer. Nutrient addition weakly affected the herbivore assemblage, not affecting richness and increasing total abundance by increasing one herbivore species (Caprella sp.). Nutrient addition did not affect beta diversity.
5.We demonstrated that assemblage‐level effects of trophic manipulations on community structure are the result of distinct and often indirect responses of herbivore species. These results underscore the importance of understanding herbivore‐herbivore interactions in a system commonly subjected to both eutrophication and overfishing.
This article is protected by copyright. All rights reserved.PubDate: 2015-02-09T00:51:52.168881-05:DOI: 10.1111/1365-2656.12350

Authors:Rui‐Wu Wang; Bao‐Fa Sun, Yan YangPages: n/a - n/aAbstract: 1.Sanctioning or punishing are regarded as one of most important dynamics in the evolution of cooperation. However, it has not been empirically examined yet whether or not such enforcement selection by sanctioning or punishing and classical theories like kin or reciprocity selection are separate mechanisms contributing to the evolution of cooperation. In addition, it remains largely unclear what factors determine the intensity or effectiveness of sanction.
2.Here we show that in the obligate, inter‐specific cooperation between figs and fig wasps, the hosted figs can discriminatively sanction cheating individuals by decreasing the offspring development ratio. Concurrently, the figs can reward the cooperative pollinators with a higher offspring development ratio. This sanction intensity and effectiveness largely depend on how closely the host and symbiont are related either in terms of reciprocity exchange or genetic similarity as measured by the reciprocal of the foundress number.
3.Our results imply that in asymmetric systems, symbionts might be forced to evolve to be cooperative or even altruistic through discriminative sanction against the non‐cooperative symbiont and reward to the cooperative symbiont by the host (i.e., through a game of “carrot and stick”).
This article is protected by copyright. All rights reserved.PubDate: 2015-02-09T00:51:36.547257-05:DOI: 10.1111/1365-2656.12351

Authors:David J. Lawrence; David A. Beauchamp, Julian D. OldenAbstract: Many ecologists have called for mechanism‐based investigations to identify the underlying controls on species distributions. Understanding these controls can be especially useful to construct robust predictions of how a species range may change in response to climate change or the extent to which a non‐native species may spread in novel environments.
Here we link spatially‐intensive observations with mechanistic models to illustrate how physiology determines the upstream extent of the aquatic ectotherm smallmouth bass (Micropterus dolomieu) in two headwater rivers.
Our results demonstrate that as temperatures become increasingly cold across a downstream to upstream gradient, food consumption in age 0 bass becomes increasingly constrained, and as a result, these fish become growth limited. Sufficient first summer growth of age 0 bass is essential for overwinter survival because young bass must persist from energy reserves accumulated during the summer, and those reserves are determined by body size.
Our field data reveals the upstream extent of adult bass reproduction corresponds to a point in the downstream/upstream gradient where cold temperatures impair growth opportunities in young bass. This pattern was repeated in both study streams, and explained why bass positioned nests twice as far upstream in the warm compared to the cold stream in the same basin. Placement of spawning nests by adult bass is likely subject to strong evolutionary selection in temperate systems: if bass spawn too far upstream their young are unlikely to grow large enough to survive the winter. Consumption and growth in older bass (age 3‐4) was far less sensitive to temperature. Based on these data we suggest that temperature‐sensitive age 0 bass constrain the upstream distribution limits of bass within temperate streams.
In this study we investigated how temperature‐dependent physiology changed through the life history of a species, and in doing so, identified a climate‐sensitive life history stage that likely sets the distributional limits of all other life history stages. We anticipate the framework developed here could be employed to identify how similar stage‐specific environmental sensitivity determines distribution in many other ectothermic species.
This article is protected by copyright. All rights reserved.PubDate: 2015-02-06T07:01:27.360108-05:DOI: 10.1111/1365-2656.12332

Authors:Brittany F. Sears; Paul W. Snyder, Jason R. RohrAbstract: There is growing interest in the role that life‐history traits of hosts, such as their “pace‐of‐life”, play in the evolution of resistance and tolerance to parasites.
Theory suggests that, relative to host species that have high syntopy (local spatial and temporal overlap) with parasites, host species with low syntopy should have lower selection pressures for more constitutive (always present) and costly defenses, such as tolerance, and greater reliance on more inducible and cheaper defenses, such as behavior. Consequently, we postulated that the degree of host‐parasite syntopy, which is negatively correlated with host pace‐of‐life (an axis reflecting the developmental rate of tadpoles and the inverse of their size at metamorphosis) in our tadpole‐parasitic cercarial (trematode) system, would be a negative and positive predictor of behavioral resistance and tolerance, respectively.
To test these hypotheses, we exposed seven tadpole species to a range of parasite (cercarial) doses crossed with anesthesia treatments that controlled for anti‐parasite behavior. We quantified host behavior, successful and unsuccessful infections, and each species’ reaction norm for behavioral resistance and tolerance, defined as the slope between cercarial exposure (or attempted infections) and anti‐cercarial behaviors and mass change, respectively. Hence, tolerance is capturing any cost of parasite exposure.
As hypothesized, tadpole pace‐of‐life was a significant positive predictor of behavioral resistance and negative predictor of tolerance, a result that is consistent with a trade‐off between behavioral resistance and tolerance across species that warrants further investigation. Moreover, these results were robust to considerations of phylogeny, all possible re‐orderings of the three fastest‐ or slowest‐paced species, and various measurements of tolerance.
These results suggest that host pace‐of‐life and host‐parasite syntopy are powerful drivers of both the strength and type of host defense strategies against parasites. Future research should evaluate how often and how strongly host pace‐of‐life and host‐parasite syntopy are correlated and which is the better predictor of the strength and type of host investments in anti‐parasite defenses.
This article is protected by copyright. All rights reserved.PubDate: 2015-02-04T00:58:01.019305-05:DOI: 10.1111/1365-2656.12333

Authors:Panu Välimäki; Sami M. Kivelä, Jani Raitanen, Veli‐Matti Pakanen, Emma Vatka, Maarit I. Mäenpää, Netta Keret, Toomas TammaruAbstract: 1.Spatio‐temporal variation in the degree of melanism is often considered in the context of thermal adaptation, melanism being advantageous under suboptimal thermal conditions. Yet, other mutually non‐exclusive explanations exist. Analysis of geographical patterns combined with laboratory experiments on the mechanisms of morph induction helps to unveil the adaptive value of particular cases of polyphenism.
2.In the context of the thermal melanism hypothesis and seasonal adaptations, we explored an array of environmental factors that may affect the expression and performance of non‐melanic vs. melanic larval morphs in different latitudinal populations of the facultatively bivoltine moth Chiasmia clathrata (Lepidoptera: Geometridae).
3.Geographic variation in larval coloration was independent of average temperatures experienced by the populations in the wild. The melanic morph was, however, more abundant in dry than in mesic habitats. In the laboratory, the melanic morph was induced especially under a high level of incident radiation but also at relatively high temperatures, but independently of photoperiod. Melanic larvae had higher growth rates and shorter development times than the non‐melanic ones when both temperature and the level of incident radiation were high.
4.Our results that melanism is induced and advantageous in warm desiccating conditions contradict the thermal melanism hypothesis for this species. Neither has melanism evolved to compensate time constraints due to forth‐coming autumn. Instead, larvae solve seasonal variation in the time available for growth by an elevated growth rate and a shortened larval period in the face of autumnal photoperiods. The phenotypic response to the level of incident radiation and a lack of adaptive adjustment of larval growth trajectories in univoltine populations underpin the role of deterministic environmental variation in the evolution of irreversible adaptive plasticity and seasonal polyphenism.
This article is protected by copyright. All rights reserved.PubDate: 2015-02-04T00:25:25.785393-05:DOI: 10.1111/1365-2656.12330

Authors:Martin Volf; Jan Hrcek, Riitta Julkunen‐Tiitto, Vojtech NovotnyAbstract: 1.Plant‐insect food webs tend to be dominated by interactions resulting from diffuse coevolution between plants and multiple lineages of herbivores rather than by reciprocal coevolution and co‐cladogenesis. Plants therefore require defence strategies effective against a broad range of herbivore species. In one extreme, plants could develop a single universal defence effective against all herbivorous insects, or tailor‐made strategies for each herbivore species. The evolution and ecology of plant defence has to be studied with entire insect assemblages, rather than small subsets of pairwise interactions.
2.The present study examines whether specialists and generalists in three coexisting insect lineages, forming the leaf‐chewing guild, respond uniformly to plant phylogeny, secondary metabolites, nutrient content and mechanical anti‐herbivore defences of their hosts, thus permitting universal plant defence strategies against specialised and generalist folivorous insects from various taxa.
3.The extensive data on folivorous assemblages comprising three insect orders and 193 species are linked with plant phylogeny, secondary chemistry (salicylates, flavonoids and tannins), leaf morphological traits (SLA and trichome coverage), nutrient (C:N) content and growth‐form of eight willow (Salix) and one aspen (Populus) species growing in sympatry.
4.Generalists responded to overall host‐plant chemistry and trichomes, whilst specialists responded to host‐plant phylogeny and secondary metabolites that are unique to willows and that are capable of being utilised as an anti‐predator protection. We did not find any significant impact of other plant traits, i.e. specific leaf area, C:N ratio, flavonoids, tannins and growth‐form, on the composition of leaf‐chewing communities.
5.Our results show that the response to plant traits is differential among specialists and generalists. This finding constrains the ability of plants to develop defensive traits universally effective against herbivores and may lead to diversification of plant defensive mechanisms into several complementary syndromes, required for effective protection against generalists and specialists from multiple insect taxa comprising most leaf‐chewing assemblages. These results point to the necessity of broad studies of plant‐herbivore interactions, across multiple insect taxa and guilds.
This article is protected by copyright. All rights reserved.PubDate: 2015-02-03T11:01:31.05106-05:0DOI: 10.1111/1365-2656.12349

Authors:Brittany H. Ousterhout; Thomas L. Anderson, Dana L. Drake, William E. Peterman, Raymond D. SemlitschAbstract: 1.In recent studies habitat traits have emerged as stronger predictors of species occupancy, abundance, richness and diversity than competition. However, in many cases it remains unclear whether habitat also mediates processes more subtle than competitive exclusion, such as growth, or if intra‐ and interspecific interactions among individuals of different species may be a better predictor of size.
2.To test whether habitat traits are a stronger predictor of abundance and body size than intra‐ and interspecific interactions, we measured the density and body size of three species of larval salamanders in 192 ponds across a landscape.
3.We found that the density of larvae was best predicted by models that included habitat features, while models incorporating interactions among individuals of different species best explained the body size of larvae. Additionally, we found a positive relationship between focal species density and congener density, while focal species body size was negatively related to congener density.
4.We posit that salamander larvae may not experience competitive exclusion, and thus reduced densities, but instead compensate for increased competition behaviorally (e.g. reduced foraging), resulting in decreased growth. The discrepancy between larval density and body size, a strong predictor of fitness in this system, also highlights a potential shortcoming in using density or abundance as a metric of habitat quality or population health.
This article is protected by copyright. All rights reserved.PubDate: 2015-02-03T04:08:01.872334-05:DOI: 10.1111/1365-2656.12344

Authors:L. Kernaléguen; J. P. Y. Arnould, C. Guinet, Y. CherelAbstract: 1.The degree of individual specialisation in resource use differs widely among wild populations where individuals range from fully generalised to highly specialised. This inter‐individual variation has profound implications in many ecological and evolutionary processes. A recent review proposed four main ecological causes of individual specialisation: inter‐ and intra‐specific competition, ecological opportunity and predation.
2.Using the isotopic signature of sub‐sampled whiskers, we investigated to what degree three of these factors (inter‐ and intra‐specific competition and ecological opportunity) affect the population niche width and the level of individual foraging specialisation in two fur seal species, the Antarctic and subantarctic fur seals (Arctocephalus gazella and A. tropicalis), over several years.
3.Population niche width was greater when the two seal species bred in allopatry (low inter‐specific competition) than in sympatry or when seals bred in high density stabilized colonies (high intra‐specific competition). In agreement with the Niche Variation Hypothesis (NVH), higher population niche width was associated with higher inter‐individual niche variation. However, in contrast with the NVH, all Antarctic females increased their niche width during the inter‐breeding period when they had potentially access to a wider diversity of foraging grounds and associated prey (high ecological opportunities), suggesting they all dispersed to a similar productive area.
4.The degree of individual specialisation varied among populations and within the annual cycle. Highest levels of inter‐individual variation were found in a context of lower inter‐ or higher intra‐specific competition. Contrasted results were found concerning the effect of ecological opportunity. Depending on seal species, females exhibited either a greater or lower degree of individual specialisation during the inter‐breeding period, reflecting species‐specific biological constraints during that period.
5.These results suggest a significant impact of ecological interactions on the population niche width and degree of individual specialisation. Such variation at the individual level may be an important factor in the species plasticity with significant consequences on how it may respond to environmental variability.
This article is protected by copyright. All rights reserved.PubDate: 2015-02-02T09:45:42.500485-05:DOI: 10.1111/1365-2656.12347

Authors:Itsumi Nakamura; Yusuke Goto, Katsufumi SatoAbstract: 1.Ocean sunfish (Mola mola) were believed to be inactive jellyfish feeders because they are often observed lying motionless at the sea surface. Recent tracking studies revealed that they are actually deep divers, but there has been no evidence of foraging in deep water. Furthermore, the surfacing behaviour of ocean sunfish was thought to be related to behavioural thermoregulation, but there was no record of sunfish body temperature.
2.Evidence of ocean sunfish feeding in deep water was obtained using a combination of an animal‐borne accelerometer and camera with a light source. Siphonophores were the most abundant prey items captured by ocean sunfish and were typically located at a depth of 50–200 m where the water temperature wasPubDate: 2015-02-02T08:57:05.574721-05:DOI: 10.1111/1365-2656.12346

Authors:Dino P. McMahon; Matthias A. Fürst, Jesicca Caspar, Panagiotis Theodorou, Mark J. F. Brown, Robert J. PaxtonAbstract: 1.Declining populations of bee pollinators are a cause of concern, with major repercussions for biodiversity loss and food security. RNA viruses associated with honeybees represent a potential threat to other insect pollinators, but the extent of this threat is poorly understood.
2.This study aims to attain a detailed understanding of the current and on going risk of emerging infectious disease (EID) transmission between managed and wild pollinator species across a wide range of RNA viruses.
3.Within a structured large‐scale national survey across 26 independent sites, we quantify the prevalence and pathogen loads of multiple RNA viruses in co‐occurring managed honeybee (Apis mellifera) and wild bumblebee (Bombus spp.) populations. We then construct models that compare virus prevalence between wild and managed pollinators.
4.Multiple RNA viruses associated with honeybees are widespread in sympatric wild bumblebee populations. Virus prevalence in honeybees is a significant predictor of virus prevalence in bumblebees, but we remain cautious in speculating over the principle direction of pathogen transmission. We demonstrate species‐specific differences in prevalence, indicating significant variation in disease susceptibility or resilience. Pathogen loads within individual bumblebees may be high and in the case of at least one RNA virus, prevalence is higher in wild bumblebees than in managed honeybee populations.
5.Our findings indicate widespread transmission of RNA viruses between managed and wild bee pollinators, pointing to an interconnected network of potential disease pressures within and between pollinator species. In the context of the biodiversity crisis, our study emphasizes the importance of targeting a wide range of pathogens and defining host associations when considering potential drivers of population decline.
This article is protected by copyright. All rights reserved.PubDate: 2015-02-02T08:47:56.394707-05:DOI: 10.1111/1365-2656.12345

Authors:Jane M. Reid; A. Bradley Duthie, Matthew E. Wolak, Peter ArceseAbstract: 1.One hypothesis explaining extra‐pair reproduction is that socially monogamous females mate with extra‐pair males to adjust the coefficient of inbreeding (f) of extra‐pair offspring (EPO) relative to that of within‐pair offspring (WPO) they would produce with their socially‐paired male. Such adjustment of offspring f requires non‐random extra‐pair reproduction with respect to relatedness, which is in turn often assumed to require some mechanism of explicit pre‐copulatory or post‐copulatory kin discrimination.
2.We propose three demographic processes that could potentially cause mean f to differ between individual females’ EPO and WPO given random extra‐pair reproduction with available males without necessarily requiring explicit kin discrimination. Specifically, such a difference could arise if social pairings formed non‐randomly with respect to relatedness or persisted non‐randomly with respect to relatedness, or if the distribution of relatedness between females and their sets of potential mates changed during the period through which social pairings persisted.
3.We used comprehensive pedigree and pairing data from free‐living song sparrows (Melospiza melodia) to quantify these three processes and hence investigate how individual females could adjust mean offspring f through instantaneously random extra‐pair reproduction.
4.Female song sparrows tended to form social pairings with unrelated or distantly related males slightly less frequently than expected given random pairing within the defined set of available males. Furthermore, social pairings between more closely related mates tended to be more likely to persist across years than social pairings between less closely related mates. However, these effects were small and the mean relatedness between females and their sets of potential extra‐pair males did not change substantially across the years through which social pairings persisted.
5.Our framework and analyses illustrate how demographic and social structuring within populations might allow females to adjust mean f of offspring through random extra‐pair reproduction without necessarily requiring explicit kin discrimination, implying that adjustment of offspring f might be an inevitable consequence of extra‐pair reproduction. New theoretical and empirical studies are required to explore the general magnitude of such effects and the degree to which they could facilitate or constrain long‐term evolution of extra‐pair reproduction.
This article is protected by copyright. All rights reserved.PubDate: 2015-02-02T08:41:37.597953-05:DOI: 10.1111/1365-2656.12340

Authors:K. J MacLeod; K. E McGhee, T. H Clutton‐BrockAbstract: Cooperative behaviours by definition are those that provide some benefit to another individual. Allonursing, the nursing of non‐descendent young, is often considered a cooperative behavior and is assumed to provide benefits to recipient offspring in terms of growth and survival, and to their mothers, by enabling them to share the lactation load. However, these proposed benefits are not well understood, in part because maternal and litter traits and other ecological and social variables are not independent of one another, making patterns hard to discern using standard univariate analyses.
Here, we investigate the potential benefits of allonursing in the cooperatively breeding Kalahari meerkat, where socially subordinate females allonurse the young of a dominant pair without having young of their own.
We use structural equation modelling to allow us to account for the interdependence of maternal traits, litter traits and environmental factors.
We find no evidence that allonursing provides benefits to pups or mothers. Pups that received allonursing were not heavier at emergence and did not have a higher survival rate than pups that did not receive allonursing. Mothers whose litters were allonursed were not in better physical condition, did not reconceive faster, and did not reduce their own nursing investment compared to mothers who nursed their litters alone. These patterns were not significantly influenced by whether mothers were in relatively good, or poor, condition.
We suggest that allonursing may persist in this species because the costs to allonurses may be low. Alternatively allonursing may confer other, more cryptic, benefits to pups or allonurses, such as immunological or social benefits.
This article is protected by copyright. All rights reserved.PubDate: 2015-01-31T02:03:51.549794-05:DOI: 10.1111/1365-2656.12343

Authors:Maxwell J. Farrell; Patrick R. Stephens, Lea Berrang‐Ford, John L. Gittleman, T. Jonathan DaviesAbstract: Host extinction can alter disease transmission dynamics, influence parasite extinction, and ultimately change the nature of host‐parasite systems. While theory predicts that single‐host parasites are among the parasite species most susceptible to extinction following declines in their hosts, documented parasite extinctions are rare.
Using a comparative approach, we investigate how the richness of single‐host and multi‐host parasites is influenced by extinction risk among ungulate and carnivore hosts. Host‐parasite associations for free‐living carnivores (order Carnivora) and terrestrial ungulates (orders Perrisodactlya + Cetartiodactlya minus cetaceans) were merged with host trait data and IUCN Red List status to explore the distribution of single‐host and multi‐host parasites among threatened and non‐threatened hosts.
We find that threatened ungulates harbour a higher proportion of single‐host parasites compared to non‐threatened ungulates, which is explained by decreases in the richness of multi‐host parasites. However, among carnivores threat status is not a significant predictor of the proportion of single‐host parasites, or the richness of single‐host or multi‐host parasites.
The loss of multi‐host parasites from threatened ungulates may be explained by decreased cross‐species contact as hosts decline and habitats become fragmented. Among carnivores threat status may not be important in predicting patterns of parasite specificity because host decline results in equal losses of both single‐host parasites and multi‐host parasites through reduction in average population density and frequency of cross‐species contact.
Our results contrast with current models of parasite coextinction and highlight the need for updated theories that are applicable across host groups and account for both inter and intraspecific contact.
This article is protected by copyright. All rights reserved.PubDate: 2015-01-31T01:52:35.213789-05:DOI: 10.1111/1365-2656.12342

Authors:Janeene M Touchton; Martin WikelskiAbstract: Loss of a dominant competitor can open ecological opportunities. Ecological opportunities are considered prerequisites for adaptive radiations. Nonetheless, initiation of diversification in response to ecological opportunity is seldom observed, so we know little about the stages by which behavioural variation either increases or coalesces into distinct phenotypes.
Here, a natural experiment showed that in a tropical island's guild of army‐ant following birds, a new behavioural phenotype emerged in subordinate spotted antbirds (Hylophylax naevioides) after the socially dominant ocellated antbird (Phaenostictus mcleannani) died out.
Individuals with this behavioural phenotype are less territorial; instead, they roam in search of ant swarms where they feed in locations from which dominant competitors formerly excluded them. Roaming individuals fledge more young than territorial individuals.
We conclude that ecological opportunity arising from species loss may enhance the success of alternative behavioural phenotypes and can favour further intraspecific diversification in life‐history traits in surviving species.
This article is protected by copyright. All rights reserved.PubDate: 2015-01-31T01:46:49.789493-05:DOI: 10.1111/1365-2656.12341

Authors:Richard McFarland; Andrea Fuller, Robyn S. Hetem, Duncan Mitchell, Shane K. Maloney, S. Peter Henzi, Louise BarrettAbstract: Sociality has been shown to have adaptive value for gregarious species, with more socially integrated animals within groups experiencing higher reproductive success and longevity. The value of social integration is often suggested to derive from an improved ability to deal with social stress within a group; other potential stressors have received less attention.
We investigated the relationship between environmental temperature, an important non‐social stressor, and social integration in wild female vervet monkeys (Chlorocebus pygerythrus), using implanted data‐loggers to obtain direct measures of core body temperature.
Heterothermy (as measured by 24h amplitude of body temperature) increased, and 24h minima of body temperature decreased, as the 24h minimum ambient temperature decreased. As winter progressed, monkeys became increasingly heterothermic and displayed lower 24h minima of body temperature.
Monkeys with a greater number of social partners displayed a smaller 24h amplitude (that is, were more homeothermic) and higher 24h minima of body temperature (that is, became less hypothermic), than did animals with fewer social partners.
Our findings demonstrate that social integration has a direct influence on thermoregulatory ability: individual animals that form and maintain more social relationships within their group experience improved thermal competence compared to those with fewer social relationships.
Given the likely energetic consequences of thermal benefits, our findings offer a viable physiological explanation that can help account for variations in fitness in relation to individual differences in social integration.
This article is protected by copyright. All rights reserved.PubDate: 2015-01-30T04:59:50.677735-05:DOI: 10.1111/1365-2656.12329

Authors:Barbara A. Han; Andrew W. Park, A. Jolles, Sonia AltizerAbstract: 1.Animal social and movement behaviors can impact the transmission dynamics of infectious diseases, especially for pathogens transmitted through close contact between hosts or through contact with infectious stages in the environment.
2.Estimating pathogen transmission rates and R0 from natural systems can be challenging. Because host behavioral traits that underlie the transmission process vary predictably with body size, one of the best‐studied traits among animals, body size might therefore also predict variation in parasite transmission dynamics.
3.Here, we examine how two host behaviors, social group living and the intensity of habitat use, scale allometrically using comparative data from wild primate, carnivore and ungulate species. We use these empirical relationships to parameterize classical compartment models for infectious micro‐ and macroparasitic diseases, and examine how the risk of pathogen invasion changes as a function of host behavior and body size. We then test model predictions using comparative data on parasite prevalence and richness from wild mammals.
4.We report a general pattern suggesting that smaller‐bodied mammal species utilizing home ranges more intensively experience greater risk for invasion by environmentally‐transmitted macroparasites. Conversely, larger‐bodied hosts exhibiting a high degree of social group living could be more readily invaded by directly‐transmitted microparasites. These trends were supported through comparison of micro‐ and macroparasite species richness across a large number of carnivore, primate and ungulate species, but empirical data on carnivore macroparasite prevalence showed mixed results.
5.Collectively, our study demonstrates that combining host behavioral traits with dynamical models of infectious disease scaled against host body size can generate testable predictions for variation in parasite risk across species; a similar approach might be useful in future work focused on predicting parasite distributions in local host communities.
This article is protected by copyright. All rights reserved.PubDate: 2015-01-28T10:16:26.082183-05:DOI: 10.1111/1365-2656.12336

Authors:Thomas L. Anderson; Howard H. WhitemanAbstract: 1.Assessment of the relative strengths of intra‐ and interspecific competition has increased in recent years, and is critical to understanding the importance of competition. Yet, whether intra‐ and interspecific competition can have non‐additive effects has rarely been tested. The resulting fitness consequences of such non‐additive interactions are important to provide the context necessary to advance our understanding of competition theory.
2.We compared the strength of additive and non‐additive intra‐ and interspecific competition by manipulating densities of a pair of larval salamanders (Ambystoma talpoideum and A. maculatum) in experimental mesocosms within a response surface design.
3.Intraspecific density had the strongest effect on the strength of competition for both species, and few observed comparisons indicated interspecific competition was an important factor in predicting body size, growth or larval period length of either species.
4.Non‐additive effects of intra‐ and interspecific competition influenced some response variables, including size and mass at metamorphosis in A. maculatum, but at a reduced strength compared to intraspecific effects alone.
5.Intraspecific competition was thus the dominant biotic interaction, but non‐additive effects also impact the outcome of competition in these species, validating the importance of testing for and incorporating non‐additive density effects into competition models.
This article is protected by copyright. All rights reserved.PubDate: 2015-01-28T03:01:48.138107-05:DOI: 10.1111/1365-2656.12335

Authors:Pei‐Jen L. Shaner; Tzu‐Hsuan Tsao, Rong‐Chien Lin, Wei Liang, Chia‐Fen Yeh, Xiao‐Jun Yang, Fu‐Min Lei, Fang Zhou, Can‐Chao Yang, Le Manh Hung, Yu‐Cheng Hsu, Shou‐Hsien LiAbstract: Niche evolution underpins the generation and maintenance of biological diversity, but niche conservatism, in which niches remain little changed over time in closely related taxa and the role of ecology in niche evolution are continually debated.
To test whether climate niches are conserved in two closely related passerines in East Asia – the vinous‐throated (Paradoxornis webbianus) and ashy‐throated (P. alphonsianus) parrotbills – we established their potential allopatric and sympatric regions using ecological niche models and compared differences in their climate niches using niche overlap indices in background tests and multivariate statistical analyses. We also used polymorphism data on 44 nuclear genes to infer their divergence demography.
We found that these two parrotbills occupy different climate niches, in both their allopatric and potential sympatric regions. Because the potential sympatric region is the area predicted to be suitable for both parrotbills based on the ecological niche models, it can serve as a natural common garden. Therefore, their observed niche differences in this potential sympatry were not simply rendered by phenotypic plasticity, and probably had a genetic basis.
Our genetic analyses revealed that the two parrotbills are not evolutionarily independent for the most recent part of their divergence history. The two parrotbills diverged c. 856,000 years ago, and have had substantial gene flow since a presumed secondary contact c. 290,000 years ago.
This study provides an empirical case demonstrating that climate niches may not be homogenized in nascent species in spite of substantial, ongoing gene flow, which in turn suggests a role for ecology in promoting and maintaining diversification among incipient species.
This article is protected by copyright. All rights reserved.PubDate: 2015-01-13T01:28:43.896886-05:DOI: 10.1111/1365-2656.12331

Authors:Heather M. Kharouba; Mark Vellend, Rana M. Sarfraz, Judith H. MyersAbstract: 1.The phenology of many species is shifting in response to climatic changes and these shifts are occurring at varying rates across species. This can potentially affect species’ interactions and individual fitness. However, few studies have experimentally tested the influence of warming on the timing of species interactions. This is an important gap in the literature given the potential for different direct and indirect effects of temperature via phenological change.
2.Our aim was to test the effects of warming on the western tent caterpillar (Malacosoma californicum pluviale). In addition to the direct effects of warming, we considered the two primary indirect effects mediated by warming‐driven changes in its host plant, red alder (Alnus rubra): changes in resource availability due to phenological mismatch (i.e. changes in the relative timing of the interaction), and changes in resource quality associated with leaf maturation.
3.We experimentally warmed egg masses and larvae of the western tent caterpillar placed on branches of red alder in the field.
4.Warming advanced the timing of larval but not leaf emergence. This led to varying degrees of phenological mismatch, with larvae emerging as much as 25 days before to 10 days after the emergence of leaves. Even the earliest‐emerging larvae, however, had high survival in the absence of leaves for up to three weeks, and they were surprisingly resistant to starvation. In addition, although warming created phenological mismatch that initially slowed the development of larvae that emerged before leaf emergence, it accelerated larval development once leaves were available. Therefore, warming had no net effect on our measures of insect performance.
5.Our results demonstrate that the indirect effects of warming, in creating phenological mismatch, are as important to consider as the direct effects on insect performance. Although future climatic warming might influence plants and insects in different ways, some insects may be well adapted to variation in the timing of their interactions.
This article is protected by copyright. All rights reserved.PubDate: 2015-01-09T07:08:14.219539-05:DOI: 10.1111/1365-2656.12328

Authors:Jennifer J. Krauel; John K. Westbrook, Gary F. McCrackenPages: n/a - n/aAbstract: Animal migrations generate large spatial and temporal fluctuations in biomass that provide a resource base for many predator‐prey interactions. These interactions are often driven by continent‐scale weather patterns and are difficult to study. Few studies have included migratory animals on more than a single trophic level or for periods spanning multiple entire seasons.
We tracked migrations of three species of agricultural pest noctuid moths over the 2010‐2012 autumn seasons as the moths traveled past a large colony of migratory Brazilian free‐tailed bats (Tadarida brasiliensis) in Texas.
Increases in moth abundance, mass of bats, and duration of bat activity outside of the cave were correlated with passage of cold fronts over the study area and related increases in northerly wind. Moth responses to weather patterns varied among species and seasons, but overall moth abundances were low in late summer and spiked after one or more cold front passages in September and October.
Changes in bat mass and behavior appear to be consequences of bat migration, as cave use transitioned from summer maternity roost to autumn migratory stopover sites.
Weather‐driven migration is at considerable risk from climate change, and bat and moth responses to that change may have marked impacts on agricultural systems and bat ecosystem services.
This article is protected by copyright. All rights reserved.PubDate: 2014-12-10T01:16:28.287898-05:DOI: 10.1111/1365-2656.12327

Authors:Coleen C. Suckling; Melody S. Clark, Joelle Richard, Simon A. Morley, Michael A. S. Thorne, Elizabeth M. Harper, Lloyd S. PeckPages: n/a - n/aAbstract: This study examined the effects of long‐term culture under altered conditions on the Antarctic sea urchin, Sterechinus neumayeri.
Sterechinus neumayeri was cultured under the combined environmental stressors of lowered pH (−0·3 and −0·5 pH units) and increased temperature (+2 °C) for 2 years. This time‐scale covered two full reproductive cycles in this species and analyses included studies on both adult metabolism and larval development.
Adults took at least 6–8 months to acclimate to the altered conditions, but beyond this, there was no detectable effect of temperature or pH.
Animals were spawned after 6 and 17 months exposure to altered conditions, with markedly different outcomes. At 6 months, the percentage hatching and larval survival rates were greatest in the animals kept at 0 °C under current pH conditions, whilst those under lowered pH and +2 °C performed significantly less well. After 17 months, performance was not significantly different across treatments, including controls. However, under the altered conditions urchins produced larger eggs compared with control animals.
These data show that under long‐term culture adult S. neumayeri appear to acclimate their metabolic and reproductive physiology to the combined stressors of altered pH and increased temperature, with relatively little measureable effect. They also emphasize the importance of long‐term studies in evaluating effects of altered pH, particularly in slow developing marine species with long gonad maturation times, as the effects of altered conditions cannot be accurately evaluated unless gonads have fully matured under the new conditions.
This paper shows that acclimation to altered pH takes up to 8 months in Antarctic sea urchins and also that gonads matured for their full development time (2 years) in altered pH significantly enhances reproductive outcomes compared to short term exposures.PubDate: 2014-12-09T19:41:22.97748-05:0DOI: 10.1111/1365-2656.12316

Authors:Stephen M. Thomas; Thomas W. CrowtherAbstract: The stable isotopes of carbon (13C /12C) and nitrogen (15N /14N) represent powerful tools in food‐web ecology, providing a wide range of dietary information in animal consumers. However, identifying the temporal window over which a consumer's isotopic signature reflects its diet requires an understanding of elemental incorporation, a process that varies from days to years across species and tissue types.
Though theory predicts body size and temperature are likely to control incorporation rates, this has not been tested empirically across a morphologically and phylogenetically diverse range of taxa. Readily available estimates of this relationship would, however, aid in the design of stable isotope food‐web investigations and improve the interpretation of isotopic data collected from natural systems.
Using literature‐derived turnover estimates from animal species ranging in size from 1 mg to 2000 kg, we develop a predictive tool for stable isotope ecologists, allowing for estimation of incorporation rates in the structural tissues of entirely novel taxa.
In keeping with metabolic scaling theory, we show that isotopic turnover rates of carbon and nitrogen in whole organisms and muscle tissue scale allometrically with body mass raised approximately to the power ‐0.19, an effect modulated by body temperature. This relationship did not, however, apply to incorporation rates in splanchnic tissues, which were instead dependent on the thermoregulation tactic employed by an organism, being considerably faster in endotherms than ectotherms.
We believe the predictive turnover equations we provide can improve the design of experiments and interpretation of results obtained in future stable isotopic food‐web studies.
This article is protected by copyright. All rights reserved.PubDate: 2014-12-05T08:01:40.178363-05:DOI: 10.1111/1365-2656.12326

Authors:A. Cespedes; C. M. Penz, P. J. DeVriesAbstract: Flight is a key innovation in the evolutionary success of insects and essential to dispersal, territoriality, courtship and oviposition. Wing shape influences flight performance and selection likely acts to maximize performance for conducting essential behaviours that in turn results in evolution of wing shape. As wing shape also contributes to fitness, optimal shapes for particular flight behaviours can be assessed with aerodynamic predictions and placed in an ecomorphological context.
Butterflies in the tribe Haeterini (Nymphalidae) are conspicuous members of understory faunas in lowland Neotropical forests. Field observations indicate that the five genera in this clade differ in flight height and behaviour: four use gliding flight at the forest floor level, and one utilizes flapping flight above the forest floor. Nonetheless, the association of ground level gliding flight behaviour and wing shape has never been investigated in this or any other butterfly group.
We used landmark‐based geometric morphometrics to test whether wing shapes in Haeterini and their close relatives reflected observed flight behaviours. Four genera of Haeterini and some distantly related Satyrinae showed significant correspondence between wing shape and theoretical expectations in performance tradeoffs that we attribute to selection for gliding in ground effect. Forewing shape differed between sexes for all taxa, and male wing shapes were aerodynamically more efficient for gliding flight than corresponding females. This suggests selection acts differentially on male and female wing shapes, reinforcing the idea that sex‐specific flight behaviours contribute to the evolution of sexual dimorphism.
Our study indicates that wing shapes in Haeterini butterflies evolved in response to habitat‐specific flight behaviors, namely gliding in ground effect along the forest floor, resulting in ecomorphological partitions of taxa in morphospace. The convergent flight behaviour and wing morphology between tribes of Satyrinae suggests that the flight environment may offset phylogenetic constraints. Overall, this study provides a basis for exploring similar patterns of wing shape evolution in other taxa that glide in ground effect.
This article is protected by copyright. All rights reserved.PubDate: 2014-12-05T07:49:06.976472-05:DOI: 10.1111/1365-2656.12325

Authors:Florian Schwarzmüller; Nico Eisenhauer, Ulrich BroseAbstract: 1.Human activities may compromise biodiversity if external stressors such as nutrient enrichment endanger overall network stability by inducing unstable dynamics. However, some ecosystems maintain relatively high diversity levels despite experiencing continuing disturbances.
2.This indicates that some intrinsic properties prevent unstable dynamics and resulting extinctions. Identifying these “ecosystem buffers” is crucial for our understanding of the stability of ecosystems and an important tool for environmental and conservation biologists. In this vein, weak interactions have been suggested as stabilizing elements of complex systems, but their relevance has rarely been tested experimentally.
3.Here, using network and allometric theory we present a novel concept for a‐priori identification of species that buffer against externally induced instability of increased population oscillations via weak interactions. We tested our model in a microcosm experiment using a soil food‐web motif.
4.Our results show that large‐bodied species feeding at the food web's base, so called ‘trophic whales’, can buffer ecosystems against unstable dynamics induced by nutrient enrichment. Similar to the functionality of chemical or mechanical buffers, they serve as ‘biotic buffers’ that take up stressor effects and thus protect fragile systems from instability.
5.We discuss trophic whales as common functional building blocks across ecosystems. Considering increasing stressor effects under anthropogenic global change, conservation of these network‐intrinsic biotic buffers may help maintain the stability and diversity of natural ecosystems.
This article is protected by copyright. All rights reserved.PubDate: 2014-11-25T06:44:47.36788-05:0DOI: 10.1111/1365-2656.12324

Authors:Philip G. Hahn; John L. OrrockPages: n/a - n/aAbstract: Past land use can create altered soil conditions and plant communities that persist for decades, although the effects of these altered conditions on consumers are rarely investigated.
Using a large‐scale field study at 36 sites in longleaf pine (Pinus palustris) woodlands, we examined whether historic agricultural land use leads to differences in the abundance and community composition of insect herbivores (grasshoppers, families Acrididae and Tettigoniidae).
We measured the cover of six plant functional groups and several environmental variables to determine whether historic agricultural land use affects the relationships between plant cover or environmental conditions and grasshopper assemblages.
Land‐use history had taxa‐specific effects and interacted with herbaceous plant cover to alter grasshopper abundances, leading to significant changes in community composition. Abundance of most grasshopper taxa increased with herbaceous cover in woodlands with no history of agriculture, but there was no relationship in post‐agricultural woodlands. We also found that grasshopper abundance was negatively correlated with leaf litter cover. Soil hardness was greater in post‐agricultural sites (i.e. more compacted) and was associated with grasshopper community composition. Both herbaceous cover and leaf litter cover are influenced by fire frequency, suggesting a potential indirect role of fire on grasshopper assemblages.
Our results demonstrate that historic land use may create persistent differences in the composition of grasshopper assemblages, while contemporary disturbances (e.g. prescribed fire) may be important for determining the abundance of grasshoppers, largely through the effect of fire on plants and leaf litter. Therefore, our results suggest that changes in the contemporary management regimes (e.g. increasing prescribed fire) may not be sufficient to shift the structure of grasshopper communities in post‐agricultural sites towards communities in non‐agricultural habitats. Rather, repairing degraded soil conditions and restoring plant communities are likely necessary for restoring grasshopper assemblages in post‐agricultural woodlands.
This paper highlights how agricultural land‐use legacies can decouple otherwise well‐established relationships between plant productivity and herbivore abundance. These results suggest that management efforts should consider the role of historic land use on herbivore assemblages, in addition to plant communitiesPubDate: 2014-11-23T19:59:00.820726-05:DOI: 10.1111/1365-2656.12311

Authors:Stephanie A. Boudreau; Sean C. Anderson, Boris WormAbstract: 1.Exploited marine populations are thought to be regulated by the effects of fishing, species interactions, and climate. Yet it is unclear how these forces interact and vary across a species’ range.
2.We conducted a meta‐analysis of American lobster (Homarus americanus) abundance data throughout the entirety of the species’ range, testing competing hypotheses about bottom‐up (climate, temperature) versus top‐down (predation, fishing) regulation along a strong thermal gradient.
3.Our results suggest an interaction between predation and thermal range ‐ predation effects dominated at the cold and warm extremes, but not at the center of the species’ range. Similarly, there was consistent support for a positive climate effect on lobster recruitment at warm range extremes. In contrast, fishing effort followed, rather than led changes in lobster abundance over time.
4.Our analysis suggests that the relative effects of top‐down and bottom‐up forcing in regulating marine populations may intensify at thermal range boundaries, and weaken at the core of a species’ range.
This article is protected by copyright. All rights reserved.PubDate: 2014-11-21T08:52:24.021735-05:DOI: 10.1111/1365-2656.12322

Authors:Alyssa R. Cirtwill; Daniel B. StoufferAbstract: 1.Previous analyses of empirical food webs (the networks of who eats whom in a community) have revealed that parasites exert a strong influence over observed food‐web structure and alter many network properties such as connectance and degree distributions. It remains unclear, however, whether these community‐level effects are fully explained by differences in the ways that parasites and free‐living species interact within a food‐web.
2.To rigorously quantify the interrelationship between food‐web structure, the types of species in a web and the distinct types of feeding links between them, we introduce a new methodology to quantify the structural roles of both species and feeding links. Roles are quantified based on the frequencies with which a species (or link) appears in different food‐web motifs‐the building blocks of networks.
3.We hypothesised that different types of species (e.g., top predators, basal resources, parasites) and different types of links between species (e.g., classic predation, parasitism, concomitant predation on parasites along with their hosts) will show characteristic differences in their food‐web roles.
4.We found that parasites do indeed have unique structural roles in food webs. Moreover, we demonstrate that different types of feeding links (e.g., parasitism, predation, or concomitant predation) are distributed differently in a food‐web context. More than any other interaction type, concomitant predation appears to constrain the roles of parasites. In contrast, concomitant predation links themselves have more variable roles than any other type of interaction.
5.Together, our results provide a novel perspective on how both species and feeding link composition shapes the structure of an ecological community, and vice‐versa.
This article is protected by copyright. All rights reserved.PubDate: 2014-11-21T08:52:00.955938-05:DOI: 10.1111/1365-2656.12323

Authors:Priyanga AmarasekareAbstract: 1.Understanding how temperature variation influences the negative (e.g.,self‐limitation) and positive (e.g., saturating functional responses) feedback processes that characterize consumer‐resource interactions is an important research priority. Previous work on this topic has yielded conflicting out comes with some studies predicting that warming should increase consumer‐resource oscillations and others predicting that warming should decrease consumer‐resource oscillations.
2.Here I develop a consumer‐resource model that both synthesizes previous findings in a common framework and yields novel insights about temperature effects on consumer‐resource dynamics. I report three key findings. First, when the resource species’ birth rate exhibits a unimodal temperature response, as demonstrated by a large number of empirical studies, the temperature range over which the consumer‐resource interaction can persist is determined by the lower and upper temperature limits to the resource species’ reproduction. This contrasts with the prediction s of previous studies, which assume that the birth rate exhibits a monotonic temperature response, that consumer extinction is determined by temperature effects on consumer species’ traits, rather than the resource species’ traits.
3.Second, the comparative analysis I have conducted shows that whether warming leads to an increase or decrease in consumer‐resource oscillations depends on the manner in which temperature affects intra‐specific competition. When the strength of self‐limitation increases monotonically with temperature, warming causes a decrease in consumer‐resource oscillations. However, if self‐limitation is strongest at temperatures physiologically optimal for reproduction, a scenario previously unanalyzed by theory but amply substantiated by empirical data, warming can cause an increase in consumer‐resource oscillations.
4.Third, the model yields testable comparative predictions about consumer‐resource dynamics under alternative hypotheses for how temperature affects competitive and resource acquisition traits. Importantly, it does so through empirically quantifiable metrics for predicting temperature effects on consumer viability and consumer‐resource oscillations, which obviates the need for parameterizing complex dynamical models. Tests of these metrics with empirical data on a host‐parasitoid interaction yield realistic estimates of temperature limits for consumer persistence and the propensity for consumer‐resource oscillations, highlighting their utility in predicting temperature effects, particularly warming, on consumer‐resource interactions in both natural and agricultural settings.
This article is protected by copyright. All rights reserved.PubDate: 2014-11-20T09:16:07.363393-05:DOI: 10.1111/1365-2656.12320

Authors:Ivar Herfindal; Martijn Pol, Jan Tøttrup Nielsen, Bernt‐Erik Sæther, Anders Pape MøllerPages: n/a - n/aAbstract: 1.Environmental variation can induce life history changes that can last over a large part of the lifetime of an organism. If multiple demographic traits are affected, expected changes in climate may influence environmental covariances among traits in a complex manner. Thus, examining the consequences of environmental fluctuations requires that individual information at multiple life stages are available, which is particularly challenging in long‐lived species.
2.Here we analyse how variation in climatic conditions occurring in the year of hatching of female goshawks Accipiter gentilis (L.) affects age‐specific variation in demographic traits and lifetime reproductive success (LRS). LRS decreased with increasing temperature in April in the year of hatching, due to lower breeding frequency and shorter reproductive lifespan. In contrast, the probability for a female to successfully breed was higher in years with a warm April, but lower LRS of the offspring in these years generated a negative covariance among fecundity rates among generations.
3.The mechanism by which climatic conditions generated cohort effects was likely through influencing the quality of the breeding segment of the population in a given year, as the proportion of pigeons in the diet during the breeding period was positively related to annual and lifetime reproductive success, and the diet of adult females that hatched in warm years contained fewer pigeons.
4.Climatic conditions experienced during different stages of individual life histories caused complex patterns of environmental covariance among demographic traits even across generations. Such environmental covariances may either buffer or amplify impacts of climate change on population growth, emphasizing the importance of considering demographic changes during the complete life history of individuals when predicting the effect of climatic change on population dynamics of long‐lived species.
This article is protected by copyright. All rights reserved.PubDate: 2014-11-17T06:12:55.607944-05:DOI: 10.1111/1365-2656.12318

Authors:Luis J. Gilarranz; Malena Sabatino, Marcelo A. Aizen, Jordi BascomptePages: n/a - n/aAbstract: Incorporating interactions into a biogeographical framework may serve to understand how interactions and the services they provide are distributed in space.
We begin by simulating the spatiotemporal dynamics of realistic mutualistic networks inhabiting spatial networks of habitat patches. We proceed by comparing the predicted patterns with the empirical results of a set of pollination networks in isolated hills of the Argentinian Pampas.
We first find that one needs to sample up to five times as much area to record interactions as would be needed to sample the same proportion of species.
Secondly, we find that peripheral patches have fewer interactions and harbour less nested networks – therefore potentially less resilient communities – compared to central patches.
Our results highlight the important role played by the structure of dispersal routes on the spatial distribution of community patterns. This may help to understand the formation of biodiversity hot spots.
In this paper, Gilarranz and colleagues unveil the significant role played by the spatial structure of the landscape in shaping the networks of interactions between species. Their work provides further understanding of the spatial distribution of ecosystem services that help to stabilize ecological communities.PubDate: 2014-11-17T05:57:26.178903-05:DOI: 10.1111/1365-2656.12304

Authors:Alison B. Duncan; Philip Agnew, Valérie Noel, Yannis MichalakisAbstract: 1)Co‐infections may modify parasite transmission opportunities directly as a consequence of interactions in the within host environment, but also indirectly through changes in host life‐history. Furthermore, host and parasite traits are sensitive to the abiotic environment with variable consequences for parasite transmission in co‐infections.
(2)We investigate how co‐infection of the mosquito Aedes aegypti with two microsporidian parasites (Vavraia culicis and Edhazardia aedis) at two levels of larval food availability affects parasite transmission directly, and indirectly through effects on host traits
(3)In a laboratory infection experiment we compared how co‐infection, at low and high larval food availability, affected the probability of infection, within‐host growth and the transmission potential of each parasite, compared to single infections. Horizontal transmission was deemed possible for both parasites when infected hosts died harbouring horizontally‐transmitting spores. Vertical transmission was judged possible for E. aedis when infected females emerged as adults. We also compared the total input number of spores used to seed infections with output number, in single and co‐infections for each parasite.
(4)The effects of co‐infection on parasite fitness were complex, especially for V. culicis. In low larval food conditions, co‐infection increased the chances of mosquitoes dying as larvae or pupae, thus increasing opportunities for V. culicis’ horizontal transmission. However, co‐infection reduced larval longevity and hence time available for V. culicis spore production. Overall there was a negative net effect of co‐infection on V. culicis whereby the number of spores produced was less than the number used to seed infection. Co‐infections also negatively affected horizontal transmission of the more virulent parasite, E. aedis, through reduced longevity of pre‐adult hosts. However, its potential transmission suffered less relative to V. culicis.
(5)Our results show that co‐infection can negatively affect parasite transmission opportunities, both directly as well as indirectly via effects on host life‐history. We also find that transmission is contingent on the combined effect of the abiotic environment.
This article is protected by copyright. All rights reserved.PubDate: 2014-11-15T02:56:16.770584-05:DOI: 10.1111/1365-2656.12302

Authors:Cindy Gidoin; Lionel Roques, Thomas BoivinAbstract: 1.Theories of species coexistence and invasion ecology are fundamentally connected and provide a common theoretical framework for studying the mechanisms underlying successful invasions and their ecological impacts. Temporal fluctuations in resource availability and differences in life‐history traits between invasive and resident species are considered as likely drivers of the dynamics of invaded communities. Current critical issues in invasion ecology thus relate to the extent to which such mechanisms influence coexistence between invasive and resident species, and to the ability of resident species to persist in an invasive‐dominated ecosystem.
2.We tested how a fluctuating resource and species traits differences may explain and help predict long‐term impacts of biological invasions in forest specialist insect communities. We used a simple invasion system comprising closely related invasive and resident seed‐specialized wasps (Hymenoptera: Torymidae) competing for a well‐known fluctuating resource, and displaying divergent diapause, reproductive and phenological traits.
3.Based on extensive long‐term field observations (1977‐2010), we developed a combination of mechanistic and statistical models aiming to (i) obtain a realistic description of the population dynamics of these interacting species over time, and (ii) clarify the respective contributions of fluctuation‐dependent and fluctuation‐independent mechanisms to long‐term impact of invasion on the population dynamics of the resident wasp species.
4.We showed that a fluctuation‐dependent mechanism was unable to promote coexistence of the resident and invasive species. Earlier phenology of the invasive species was the main driver of invasion success, enabling the invader to exploit an empty niche. Phenology also had the greatest power to explain the long‐term negative impact of the invasive on the resident species, through resource preemption.
5.This study provides strong support for the critical role of species differences in interspecific competition outcomes within animal communities. Our mechanisticstatistical approach allows disentangling the critical drivers of the dynamics of coexistence and exclusion within novel species assemblages, following both intentional and non‐intentional species introductions.
This article is protected by copyright. All rights reserved.PubDate: 2014-11-15T02:16:42.34124-05:0DOI: 10.1111/1365-2656.12303

Authors:He Zhang; Oscar Vedder, Peter H. Becker, Sandra BouwhuisPages: n/a - n/aAbstract: 1.Within populations, the expression of phenotypic traits typically varies with age. Such age‐dependent trait variation can be caused by within‐individual change (improvement, senescence, terminal effects) and/or selective (dis)appearance of certain phenotypes among older age classes.
2.In this study we applied two methods (decomposition and mixed‐modelling) to attribute age‐dependent variation in seven phenological and reproductive traits to within‐individual change and selective (dis)appearance, in a long‐lived seabird, the common tern (Sterna hirundo).
3.At the population level, all traits, except the probability to breed, improved with age (i.e., phenology advanced and reproductive output increased). Both methods identified within‐individual change as the main responsible process, and within individuals, performance improved until age 6‐13, before levelling off. In contrast, within individuals, breeding probability decreased to age 10, then levelled off.
4.Effects of selective appearance and disappearance were small, but showed that longer‐lived individuals had a higher breeding probability and bred earlier, and that younger recruits performed better throughout life than older recruits in terms of both phenology and reproductive performance. In the year prior to death, individuals advanced reproduction, suggesting terminal investment.
5.The decomposition method attributed more age‐dependent trait variation to selective disappearance than the mixed‐modelling method: 14‐36% versus 0‐8%, respectively, which we identify to be due to covariance between rates of within‐individual change and selective (dis)appearance leading to biased results from the decomposition method.
6.We conclude that the decomposition method is ideal for visualising processes underlying population change in performance from one age class to the next, but that a mixed‐modelling method is required to investigate the significance and relative contribution of age‐effects.
7.Considerable variation in the contribution of the different age‐processes between the seven phenotypic traits studied, as well as notable differences between species in patterns of age‐dependent trait expression, calls for better predictions regarding optimal allocation strategies with age.
This article is protected by copyright. All rights reserved.PubDate: 2014-11-14T09:03:19.033941-05:DOI: 10.1111/1365-2656.12321

Authors:María Alejandra Maglianesi; Katrin Böhning–Gaese, Matthias SchleuningPages: n/a - n/aAbstract: 1.In plant–pollinator networks, the floral morphology of food plants is an important determinant of the interaction niche of pollinators. Studies on foraging preferences of pollinators combining experimental and observational approaches may help to understand the mechanisms behind patterns of interactions and niche partitioning within pollinator communities.
2.In this study, we tested whether morphological floral traits were associated with foraging preferences of hummingbirds for artificial and natural flower types in Costa Rica. We performed field experiments with artificial feeders, differing in length and curvature of flower types, to quantify the hummingbirds’ interaction niche under unlimited nectar resources. To quantify the interaction niche under real–world conditions of limited nectar resources, we measured foraging preferences of hummingbirds for a total of 34 plant species.
3.Artificial feeders were visited by Eupherusa nigriventris and Phaethornis guy in the pre–montane forest, and Lampornis calolaemus in the lower montane forest. Under experimental conditions, all three hummingbird species overlapped their interaction niches and showed a preference for the short artificial flower type over the long–straight and the long–curved flower types. Under natural conditions, the two co–occurring hummingbird species preferred to feed on plant species with floral traits corresponding to their bill morphology. The short–billed hummingbird E. nigriventris preferred to feed on short and straight flowers, whereas the long– and curved–billed P. guy preferred long and curved natural flowers. The medium–size billed species L. calolaemus preferred to feed on flowers of medium length and did not show preferences for plant species with specific corolla curvature.
4.Our results show that floral morphological traits constrain access by short–billed hummingbird species to nectar resources. Morphological constraints, therefore, represent one important mechanism structuring trophic networks. In addition, other factors, such as competition and differences in resource quantity or quality, define the interaction niches of consumer species in real–world communities, enforcing patterns of niche segregation between co–occurring consumer species. This suggests that experimental studies are needed to disentangle effects of morphological constraints from those of competition for resources in plant–pollinator interactions and other types of trophic interactions.
This article is protected by copyright. All rights reserved.PubDate: 2014-11-14T09:00:57.318896-05:DOI: 10.1111/1365-2656.12319

Authors:Aabir Banerji; Alison B. Duncan, Joanne S. Griffin, Stuart Humphries, Owen L. Petchey, Oliver KaltzAbstract: 1.Despite growing interest in ecological consequences of parasitism in food webs, relatively little is known about effects of parasites on long‐term population dynamics of non‐host species or about whether such effects are density‐ or trait‐ mediated.
2.We studied a tri‐trophic food chain comprised of: (i) a bacterial basal resource (Serratia fonticola), (ii) an intermediate consumer (Paramecium caudatum), (iii) a top predator (Didinium nasutum), and (iv) a parasite of the intermediate consumer (Holospora undulata). A fully‐factorial experimental manipulation of predator and parasite presence/absence was combined with analyses of population dynamics, modelling, and analyses of host (Paramecium) morphology and behavior.
3.Predation and parasitism each reduced the abundance of the intermediate consumer (Paramecium), and parasitism indirectly reduced the abundance of the basal resource (Serratia). However, in combination, predation and parasitism had non‐additive effects on the abundance of the intermediate consumer, as well as on that of the basal resource. In both cases, the negative effect of parasitism seemed to be effaced by predation.
4.Infection of the intermediate consumer reduced predator abundance. Modelling and additional experimentation revealed that this was most likely due to parasite reduction of intermediate host abundance (a density‐mediated effect), as opposed to changes in predator functional or numerical response.
5.Parasitism altered morphological and behavioural traits, by reducing host cell length and increasing the swimming speed of cells with moderate parasite loads. Additional tests showed no significant difference in Didinium feeding rate on infected and uninfected hosts, suggesting that the combination of these modifications does not affect host vulnerability to predation. However, estimated rates of encounter with Serratia based on these modifications were higher for infected Paramecium than for uninfected Paramecium.
6.A mixture of density‐mediated and trait‐mediated indirect effects of parasitism on non‐host species creates rich and complex possibilities for effects of parasites in food webs that should be included in assessments of possible impacts of parasite eradication or introduction.
This article is protected by copyright. All rights reserved.PubDate: 2014-11-07T10:00:45.979214-05:DOI: 10.1111/1365-2656.12317

Authors:Emanuel A. Fronhofer; Tabea Kropf, Florian AltermattAbstract: 1.Movement and dispersal are critical processes for almost all organisms in natural populations. Understanding their causes and consequences is therefore of high interest. While both theoretical and empirical work suggests that dispersal, more exactly emigration, is plastic and may be a function of local population density, the functional relationship between the underlying movement strategies and population density has received less attention.
2.We here present evidence for the shape of this reaction norm and are able to differentiate between three possible cues: the relative number of individuals, the presence of metabolites (chemical cues) and resource availability.
3.We performed microcosm experiments with the ciliate model organism Tet‐rahymena in order to understand the plasticity of movement strategies with respect to local density while controlling for possible confounding effects mediated by the availability of different cues. In addition, we investigated how an Allee effect can influence movement and dispersal plasticity.
4.Our findings suggest that movement strategies in Tetrahymena are plastic and density‐dependent. The observed movement reaction norm was ushaped. This may be due to an Allee effect which led to negative densitydependence at low population densities and generally positive density‐dependence
at high population densities due to local competition. This possibly adaptive density‐dependent movement strategy was likely mediated by chemical cues.
5.Our experimental work in highly controlled conditions indicates that both environmental cues as well as inherent population dynamics must be considered to understand movement and dispersal.
This article is protected by copyright. All rights reserved.PubDate: 2014-11-06T01:51:59.807768-05:DOI: 10.1111/1365-2656.12315

Authors:Erik Joaquín Torres‐Romero; Miguel Á. Olalla‐TárragaAbstract: Different hypotheses (geographic, ecological, evolutionary or a combination of them) have been suggested to account for the spatial variation in species richness. However, the relative importance of environment and human impacts in explaining these patterns, either globally or at the biogeographic region level, remains largely unexplored.
Here we jointly evaluate how current environmental conditions and human impacts shape global and regional gradients of species richness in terrestrial mammals.
We processed IUCN global distributional data for 3939 mammal species and a set of seven environmental and two human impact variables at a spatial resolution of 96.5x 96.5 km. We used simple, multiple and partial regression techniques to evaluate environmental and human effects on species richness.
Actual evapotranspiration is the main driver of mammal species richness globally. Together with our results at the biogeographic realm level, this lends strong support for the Hawkins et al. (2003) conjecture (i.e. global diversity gradients are best explained by the interaction of water and energy, with a latitudinal shift in the relative importance of ambient energy vs. water as we move from the poles to the equator).
While human effects on species richness are not easily detected at a global scale due to the large proportion of shared variance with the environment, these effects significantly emerge at the regional level. In the Nearctic, Palearctic and Oriental regions, the independent contribution of human impacts is almost as important as current environmental conditions in explaining richness patterns. The intersection of human impacts with climate drives the geographic variation in mammal species richness in the Palearctic, Nearctic and Oriental regions. Using a human accessibility variable we show, for the first time, that the zones most accessible to humans are often those where we find lower mammal species richness.
This article is protected by copyright. All rights reserved.PubDate: 2014-10-30T02:21:27.905553-05:DOI: 10.1111/1365-2656.12313

Authors:Michael A. Tabak; Sally Poncet, Ken Passfield, Jacob R. Goheen, Carlos Martinez del RioAbstract: Norway rats (Rattus norvegicus) were introduced to the Falkland Islands and are detrimental to native passerines. Rat eradication programs are being used to help protect the avifauna.
The present study assesses the effectiveness of eradication programs while using this conservation practice as a natural experiment to explore the ecological resistance, resilience, and homeostasis of bird communities.
We conducted bird surveys on 230 islands: 85 in the presence of rats, 108 that were historically free of rats, and 37 from which rats had been eradicated. Bird detection data were used to build occupancy models for each species and estimate species‐area relationships. Count data were used to estimate relative abundance and community structure.
Islands with invasive rats had reduced species richness of passerines and a different community structure than islands on which rats were historically absent. Although the species richness of native passerines was remarkably similar on eradicated and historically rat‐free islands, community structure on eradicated islands was more similar to that of rat‐infested islands than to historically rat‐free islands.
The results suggest that in the Falkland Islands, species richness of passerines is not resistant to invasive rats, but seems to be resilient following their removal. In contrast, community structure seems to be neither resistant nor resilient. From a conservation perspective, rat eradication programs in the Falkland Islands appear to be effective at restoring native species richness, but they are not necessarily beneficial for species of conservation concern. For species that do not recolonize, translocations following eradications may be necessary.
This article is protected by copyright. All rights reserved.PubDate: 2014-10-30T02:16:02.78452-05:0DOI: 10.1111/1365-2656.12312

Authors:S.R. Hoy; S.J. Petty, A. Millon, D.P. Whitfield, M. Marquiss, M. Davison, X. LambinAbstract: Currently, there is no general agreement about the extent to which predators’ impact prey population dynamics, as it is often poorly predicted by predation rates and species abundances. This could in part be caused by variation in the type of selective predation occurring. Notably, if predation is selective on categories of individuals that contribute little to future generations, it may moderate the impact of predation on prey population dynamics. However, despite its prevalence, selective predation has seldom been studied in this context.
Using recoveries of ringed tawny owls (Strix aluco) predated by ‘superpredators’, northern goshawks (Accipiter gentilis) as they colonised the area, we investigated the extent to which predation was sex and age‐selective. Predation of juvenile owls was disproportionately high. Amongst adults, predation was strongly biased towards females and predation risk appeared to increase with age. This implies age‐selective predation may shape the decline in survival with age, observed in tawny owls.
To determine whether selective predation can modulate the overall impact of predation, age‐based population matrix models were used to simulate the overall impact of five different patterns of age‐selective predation, including the pattern actually observed in the study site. The impact on owl population size varied by up to 50%, depending on the pattern of selective predation. The simulation of the observed pattern of predation had a relatively small impact on population size, close to the least harmful scenario, predation on juveniles only.
The actual changes in owl population size and structure, observed during goshawk colonisation were also analysed. Owl population size and immigration were unrelated to goshawk abundance. However, goshawk abundance appeared to interact with owl food availability to have a delayed effect on recruitment into the population.
This study provides strong evidence to suggest that predation of other predators is both age and sex‐selective and that selective predation of individuals with a low reproductive value may mitigate the overall impact of predators on prey population dynamics. Consequently, our results highlight how accounting for the type of selective predation occurring is likely to improve future predictions of the overall impact of predation.
This article is protected by copyright. All rights reserved.PubDate: 2014-10-21T08:32:31.258082-05:DOI: 10.1111/1365-2656.12310

Authors:Benjamin H. Letcher; Paul Schueller, Ronald Bassar, Keith H. Nislow, Jason A. Coombs, Krzysztof Sakrejda, Michael Morrissey, Douglas Sigourney, Andrew R. Whiteley, Matthew O'Donnell, Todd DubreuilAbstract: 1.Modeling the effects of environmental change on populations is a key challenge for ecologists, particularly as the pace of change increases. Currently, modeling efforts are limited by difficulties in establishing robust relationships between environmental drivers and population responses.
2.We developed an integrated capture‐recapture state‐space model to estimate the effects of two key environmental drivers (stream flow and temperature) on demographic rates (body growth, movement, and survival) using a long‐term (11 years), high resolution (individually tagged, sampled seasonally) dataset of brook trout (Salvelinus fontinalis) from four sites in a stream network. Our integrated model provides an effective context within which to estimate environmental driver effects because it takes full advantage of data by estimating (latent) state values for missing observations, because it propagates uncertainty among model components and because it accounts for the major demographic rates and interactions that contribute to annual survival.
3.We found that stream flow and temperature had strong effects on brook trout demography. Some effects, such as reduction in survival associated with low stream flow and high temperature during the summer season, were consistent across sites and age‐classes, suggesting that they may serve as robust indicators of vulnerability to environmental change. Other survival effects varied across ages, sites, and seasons, indicating that flow and temperature may not be the primary drivers of survival in those cases. Flow and temperature also affected body growth rates; these responses were consistent across sites but differed dramatically between age‐classes and seasons. Finally, we found that tributary and mainstem sites responded differently to variation in flow and temperature.
4.Annual survival (combination of survival and body growth across seasons) was insensitive to body growth and was most sensitive to flow (positive) and temperature (negative) in the summer and fall.
5.These observations, combined with our ability to estimate the occurrence, magnitude and direction of fish movement between these habitat types, indicated that heterogeneity in response may provide a mechanism providing potential resilience to environmental change. Given that the challenges we faced in our study are likely to be common to many intensive datasets, the integrated modeling approach could be generally applicable and useful.
This article is protected by copyright. All rights reserved.PubDate: 2014-10-18T05:20:11.728628-05:DOI: 10.1111/1365-2656.12308

Authors:Sjoerd Duijns; Ineke E. Knot, Theunis Piersma, Jan A. van GilsAbstract: 1.Mechanistic insights and predictive understanding of the spatial distributions of foragers are typically derived by fitting either field measurements on intake rates and food abundance, or observations from controlled experiments, to functional response models. It has remained unclear, however, whether and why one approach should be favoured above the other, as direct comparative studies are rare.
2.The field measurements required to parameterize either single or multi‐species functional response models are relatively easy to obtain, except at sites with low food densities and at places with high food densities, as the former will be avoided and the second will be rare. Also, in foragers facing a digestive bottleneck, intake rates (calculated over total time) will be constant over a wide range of food densities. In addition, interference effects may further depress intake rates. All of this hinders the appropriate estimation of parameters such as the ‘instantaneous area of discovery’ and the handling time, using a type II functional response model also known as ‘Holling's disc equation’.
3.Here we compare field‐ and controlled experimental measurements of intake rate as a function of food abundance in female bar‐tailed godwits Limosa lapponica feeding on lugworms Arenicola marina.
4.We show that a fit of the type II functional response model to field measurements predicts lower intake rates (about 2.5 times), longer handling times (about 4 times) and lower ‘instantaneous areas of discovery’ (about 30 to 70 times), compared with measurements from controlled experimental conditions.
5.In agreement with the assumptions of Holling's disc equation, under controlled experimental settings both the instantaneous area of discovery and handling time remained constant with an increase in food density. The field data, however, would lead us to conclude that although handling time remains constant, the instantaneous area of discovery decreased with increasing prey densities. This will result into highly underestimated sensory capacities when using field data.
6.Our results demonstrate that the elucidation of the fundamental mechanisms behind prey detection and prey processing capacities of a species necessitates measurements of functional response functions under the whole range of prey densities on solitary feeding individuals, which is only possible under controlled conditions. Field measurements yield ‘consistency tests’ of the distributional patterns in a specific ecological context.
This article is protected by copyright. All rights reserved.PubDate: 2014-10-18T05:20:08.533949-05:DOI: 10.1111/1365-2656.12309

Authors:Jiang‐Hui Bian; Shou‐Yang Du, Yan Wu, Yi‐Fan Cao, Xu‐Heng Nie, Hui He, Zhi‐Bing YouAbstract: 1.The hypothesis that maternal effects act as an adaptive bridge in translating maternal environments into offspring phenotypes and thereby affecting population dynamics has not been studied in the well‐controlled fields.
2.In this study, the effects of maternal population‐density on offspring stress axis, reproduction and population dynamics were studied in root voles (Microtus oeconomus). Parental enclosures for breeding offspring were established by introducing 6 adults per sex into each of 4 (low density) and 30 adults per sex into each of another 4 (high density) enclosures. Live‐trapping started 2 weeks after. Offspring captured at age of 10‐20 days were removed to laboratory, housed under laboratory conditions until puberty, and subsequently used to establish offspring populations in these same enclosures, after parental populations had been removed. Offspring from each of the 2 parental sources were assigned into 4 enclosures with 2 for each of the 2 density treatments used in establishing parental populations (referred to as LL and LH for maternally‐unstressed offspring, assigned in low‐ and high‐density, and HL and HH for maternally‐stressed offspring, assigned in low‐ and high‐density). Fecal corticosterone metabolites (FCM) levels, offspring reproduction traits and population dynamics were tested following repeated live‐trapping over 2 seasons.
3.Differential fluctuations in population size were observed between maternally density‐stressed and unstressed offspring. Populations in LL and LH groups changed significantly in responding to initial density, and reached the similar levels at beginning of the second trapping season. Populations in HL and HH groups, however, were remained relatively steady, and in HL group the low population size was sustained until end of experiment. Maternal density‐stress was associated with FCM elevations, reproduction suppression, and body mass decrease at sexual maturity in offspring. The FCM elevations and reproduction suppression were independent of offspring population density and correlated with decreased offspring quality.
4.These findings indicate that intrinsic state alterations induced by maternal stress impair offspring capacity in response to immediate environment, and these alterations are likely mediated by maternal stress system. The maladaptive reproduction suppression seen in HL group suggests intrinsic population density as one of ecological factors generating delayed density‐dependent effects.
This article is protected by copyright. All rights reserved.PubDate: 2014-10-18T05:19:33.650264-05:DOI: 10.1111/1365-2656.12307

Authors:Hanna ten Brink; Abul Kalam Azad Mazumdar, Joseph Huddart, Lennart Persson, Tom C. CameronAbstract: 1.Coexistence of predators that share the same prey is common. This is still the case in size structured predator communities where predators consume prey species of different sizes (interspecific prey responses) or consume different size classes of the same species of prey (intraspecific prey responses).
2.A mechanism has recently been proposed to explain coexistence between predators that differ in size but share the same prey species, emergent facilitation, which is dependent on strong intraspecific responses from one or more prey species. Under emergent facilitation predators can depend on each other for invasion, persistence or success in a size structured prey community.
3.Experimental evidence for intraspecific size‐structured responses in prey populations remain rare and further questions remain about direct interactions between predators that could prevent or limit any positive effects between predators (e.g. intraguild predation).
4.Here we provide a community wide experiment on emergent facilitation including natural predators. We investigate both the direct interaction between two predators that differ in body size (fish vs. invertebrate predator) and the indirect interaction between them via their shared prey community (zooplankton).
5.Our evidence supports the most likely expectation of interactions between differently sized predators, that intraguild predation rates are high and interspecific interactions in the shared prey community dominate the response to predation (i.e. predator‐mediated competition). The question of whether emergent facilitation occurs frequently in nature requires more empirical and theoretical attention, specifically to address the likelihood that its pre‐conditions may co‐occur with high rates of intraguild predation.
This article is protected by copyright. All rights reserved.PubDate: 2014-10-14T10:23:44.370185-05:DOI: 10.1111/1365-2656.12305

Authors:Jan A. Gils; Matthijs Geest, Brecht De Meulenaer, Hanneke Gillis, Theunis Piersma, Eelke O. FolmerPages: n/a - n/aAbstract: 1.Models relating intake rate to food abundance and competitor densities (generalized functional response models) can predict forager distributions and movements between patches, but we lack understanding of how distributions and small‐scale movements by the foragers themselves affect intake rates.
2.Using a state‐of‐the‐art approach based on continuous‐time Markov chain dynamics, we add realism to classic functional response models by acknowledging that the chances to encounter food and competitors are influenced by movement decisions, and, vice versa, that movement decisions are influenced by these encounters.
3.We used a multi‐state modelling framework to construct a stochastic functional response model in which foragers alternate between three behavioural states: searching, handling and moving.
4.Using behavioural observations on a molluscivore migrant shorebird (red knot, Calidris canutus canutus), at its main wintering area (Banc d'Arguin, Mauritania), we estimated transition rates between foraging states as a function of conspecific densities and densities of the two main bivalve prey.
5.Intake rate decreased with conspecific density. This interference effect was not due to decreased searching efficiency, but resulted from time lost to avoidance movements.
6.Red knots showed a strong functional response to one prey (Dosinia isocardia), but a weak response to the other prey (Loripes lucinalis). This corroborates predictions from a recently developed optimal diet model that accounts for the mildly toxic effects due to consuming Loripes.
7.Using model‐averaging across the most plausible multi‐state models, the fully parameterized functional response model was then used to predict intake rate for an independent dataset on habitat choice by red knot.
8.Comparison of the sites selected by red knots with random sampling sites showed that the birds fed at sites with higher than average Loripes and Dosinia densities, i.e. sites for which we predicted higher than average intake rates.
9.We discuss the limitations of Holling's classical functional response model that ignores movement and the limitations of contemporary movement ecological theory ignoring consumer‐resource interactions. With the rapid advancement of technologies to track movements of individual foragers at fine spatial scales, the time seems ripe to integrate descriptive tracking studies with stochastic movement‐based functional response models.
This article is protected by copyright. All rights reserved.PubDate: 2014-10-05T06:01:53.341006-05:DOI: 10.1111/1365-2656.12301

Authors:Gabriel J.Z. Colorado; Amanda D. RodewaldPages: n/a - n/aAbstract: The relative contribution of deterministic and stochastic processes in the assembly of biotic communities is a central issue of controversy in community ecology. However, several studies have shown patterns of species segregation that are consistent with the hypothesis that deterministic factors such as competition and niche‐partitioning structure species assemblages in animal communities. Community assembly provides a theoretical framework for understanding these processes, but it has been seldom applied to social aggregations within communities. In this research we assessed patterns of non‐randomness in Andean mixed‐species flocks using three assembly models: (a) co‐occurrence patterns (b) guild proportionality; and (c) constant body‐size ratios using data from 221 species of resident and Neotropical migrant birds participating in 311 mixed‐species flocks at 13 regions distributed in Venezuela, Colombia, Ecuador, and Peru. Significant assembly patterns for mixed‐species flocks based on co‐occurrence models and guild proportionality models suggest that competitive interactions play an important role in structuring this social system in the Andes. Distribution of species among foraging guilds (i.e. insectivore, frugivore, omnivore, nectivore) was generally similar among flocks, though with some regional variation. In contrast, we found little evidence that structuring of mixed‐species flocks in the Andes was mediated by body size. Rather, we found greater than expected variance of body‐size ratios within flocks, indicating that birds did not segregate morphologically. Overall, our findings suggest that deterministic factors associated to competitive interactions are important contributors to mixed‐species flock assemblages across the Andes.
This article is protected by copyright. All rights reserved.PubDate: 2014-10-05T06:01:38.704785-05:DOI: 10.1111/1365-2656.12300

Authors:Laura M. Cisneros; Matthew E. Fagan, Michael R. WilligPages: n/a - n/aAbstract: 1.Fragmentation per se due to human land conversion is a landscape‐scale phenomenon. Accordingly, assessment of distributional patterns across a suite of potentially connected communities (i.e. metacommunity structure) is an appropriate approach for understanding the effects of landscape modification, and complements the plethora of fragmentation studies that have focused on local community structure. To date, metacommunity structure within human‐modified landscapes has been assessed with regard to nestedness along species richness gradients. This is problematic because there is little support that species richness gradients are associated with the factors moulding species distributions. More importantly, many alternative patterns are possible, and different patterns may manifest during different seasons and for different guilds because of variation in resource availability and resource requirements of taxa.
2.We determined the best‐fit metacommunity structure of a phyllostomid bat assemblage, frugivore ensemble, and gleaning animalivore ensemble within a human‐modified landscape in the Caribbean lowlands of Costa Rica during the dry and wet seasons to elucidate important structuring mechanisms. Furthermore, we identified the landscape characteristics associated with the latent gradient underlying metacommunity structure.
3.We discriminated among multiple metacommunity structures by assessing coherence, range turnover, and boundary clumping of an ordinated site‐by‐species matrix. We identified the landscape characteristics associated with the latent gradient underlying metacommunity structure via hierarchical partitioning.
4.Metacommunity structure was never nested nor structured along a richness gradient.
5.The phyllostomid assemblage and frugivore ensemble exhibited Gleasonian structure (range turnover along a common gradient) during the dry season and Clementsian structure (range turnover and shared boundaries along a common gradient) during the wet season. Distance between forest patches and forest edge density structured the phyllostomid metacommunity during the dry and wet seasons, respectively. Proportion of pasture and forest patch density structured the frugivore metacommunity during the dry season.
6.Gleaning animalivores exhibited chequerboard structure (mutually exclusive species‐pairs) during the dry season and random structure during the wet season.
7.Metacommunity structure was likely mediated by differential resource use or interspecific relationships. Furthermore, the interaction between landscape characteristics and seasonal variation in resources resulted in season‐specific and guild‐specific distributional patterns.
This article is protected by copyright. All rights reserved.PubDate: 2014-10-05T06:01:23.570449-05:DOI: 10.1111/1365-2656.12299

Authors:Mariana P. Braga; Emanuel Razzolini, Walter A. BoegerPages: n/a - n/aAbstract: 1.Because host‐parasite interactions are so ubiquitous, it is of primary interest for ecologists to understand the factors that generate, maintain, and constrain these associations. Phylogenetic comparative studies have found abundant evidence for host‐switching to relatively unrelated hosts, sometimes related to diversification events, in a variety of host‐parasite systems. For Monogenoidea (Platyhelminthes) parasites, it has been suggested that the co‐speciation model alone cannot explain host occurrences, hence host‐switching and/or non‐vicariant modes of speciation should be associated with the origins and diversification of several monogenoid taxa.
2.The factors that shape broad patterns of parasite sharing were investigated using path analysis as a way to generate hypotheses about the origins of host‐parasite interactions between monogenoid gill parasites and Neotropical freshwater fishes.
3.Parasite sharing was assessed from an interaction matrix, and explanatory variables included phylogenetic relationships, environmental preferences, biological traits, and geographic distribution for each host species.
4.Although geographic distribution of hosts and host ecology are important factors to understand host‐parasite interactions, especially within host lineages that share a relatively recent evolutionary history, phylogeny had the strongest overall direct effect on parasite sharing.
5.Phylogenetic contiguity of host communities may allow a “stepping‐stone” mode of host‐switching, which increases parasite sharing. Our results reinforce the importance of including evolutionary history in the study of ecological associations, including EID risk assessment.
This article is protected by copyright. All rights reserved.PubDate: 2014-10-05T06:01:06.064332-05:DOI: 10.1111/1365-2656.12298

Authors:Matthew R. FalcyPages: n/a - n/aAbstract: 1.An extensive body of theory suggests that density‐dependent habitat selection drives many fundamental ecological processes. The ideal free distribution and the ideal despotic distribution make contrasting predictions about the effect of total population size on relative abundances among habitats. Empirical assessment of these habitat selection models is uncommon because data must be collected over large temporal and spatial scales.
2.I ask whether fluctuation in Chinook salmon (Oncorhynchus tshawytscha) spawner population size through time leads to different relative densities over space.
3.Twenty six years of monitoring data on spawning Chinook salmon across the entire coast of Oregon, USA, were used to evaluate models that make contrasting statements about the interactions of a latent population abundance parameter with physical habitat characteristics.
4.There is strong information‐theoretic support for models that include terms that allow the spatial variation in density to change as population size changes through time. Analysis of the best model reveals nonlinear isodars, which suggests a “despotic” or “preemptive” distribution of individuals across habitats, indicating that dominant or early arriving individuals exclude others from breeding sites.
5.This finding has implications for genetic dynamics, population dynamics, and conservation metrics of these highly valued fish. The novel application of modeling techniques used here to assess mechanisms of habitat selection from observational data can be used in the emerging field of eco‐evolutionary dynamics.
This article is protected by copyright. All rights reserved.PubDate: 2014-10-05T06:00:54.088917-05:DOI: 10.1111/1365-2656.12297

Authors:Guadalupe Peralta; Carol M. Frost, Raphael K. Didham, Arvind Varsani, Jason M. TylianakisAbstract: 1. Incorporating the evolutionary history of species into community ecology enhances understanding of community composition, ecosystem functioning and responses to environmental changes.
2. Phylogenetic history might partly explain the impact of fragmentation and land‐use change on assemblages of interacting organisms, and even determine potential cascading effects across trophic levels. However, it remains unclear whether phylogenetic diversity of basal resources is reflected at higher trophic levels in the food web. In particular, phylogenetic determinants of community structure have never been incorporated into habitat edge studies, even though edges are recognised as key factors affecting communities in fragmented landscapes.
3. Here we test whether phylogenetic diversity at different trophic levels (plants, herbivores, parasitoids) and signals of coevolution (i.e. phylogenetic congruence) among interacting trophic levels change across an edge gradient between native and plantation forests. To ascertain whether there is a signal of coevolution across trophic levels, we test whether related consumer species generally feed on related resource species.
4. We found differences across trophic levels in how their phylogenetic diversity responded to the habitat edge gradient. Plant and native parasitoid phylogenetic diversity changed markedly across habitats, while phylogenetic variability of herbivores (which were predominantly native) did not change across habitats, though phylogenetic evenness declined in plantation interiors. Related herbivore species did not appear to feed disproportionately on related plant species (i.e. there was no signal of coevolution) even when considering only native species, potentially due to the high trophic generality of herbivores. However, related native parasitoid species tended to feed on related herbivore species, suggesting the presence of a coevolutionary signal at higher trophic levels. Moreover, this signal was stronger in plantation forests, indicating that this habitat may impose stresses on parasitoids that constrain them to attack only host species for which they are best adapted.
5. Overall, changes in land use across native to plantation forest edges differentially affected phylogenetic diversity across trophic levels, and may also exert a strong selective pressure for particular coevolved herbivore‐parasitoid interactions.
This article is protected by copyright. All rights reserved.PubDate: 2014-10-03T06:07:08.936076-05:DOI: 10.1111/1365-2656.12296

Authors:Adam G. Hansen; David A. BeauchampAbstract: 1. Clark & Levy (1988) described an antipredation window for smaller planktivorous fish during crepuscular periods when light permits feeding on zooplankton, but limits visual detection by piscivores. Yet, how the window is influenced by the interaction between light regime, turbidity and cloud cover over a broad latitudinal gradient remains unexplored.
2. We evaluated how latitudinal and seasonal shifts in diel light regimes alter the foraging‐risk environment for visually‐feeding planktivores and piscivores across a natural range of turbidities and cloud covers. Pairing a model of aquatic visual feeding with a model of sun and moon illuminance, we estimated foraging rates of an idealized planktivore and piscivore over depth and time across factorial combinations of latitude (0‐70º), turbidity (0.1‐5 NTU) and cloud cover (clear to overcast skies) during the summer solstice and autumnal equinox. We evaluated the foraging‐risk environment based on changes in the magnitude, duration and peak timing of the antipredation window.
3. The model scenarios generated up to 10‐fold shifts in magnitude, 24‐fold shifts in duration,
and 5.5 h shifts in timing of the peak antipredation window. The size of the window increased with latitude. This pattern was strongest during the solstice. In clear water at low turbidity (0.1‐0.5 NTU), peaks in the magnitude and duration of the window formed at 57‐60º latitude, before falling to near zero as surface waters became saturated with light under a midnight sun and clear skies at latitudes near 70º. Overcast dampened the midnight sun enough to allow larger windows to form in clear water at high latitudes. Conversely, at turbidities ≥ 2 NTU, greater reductions in the visual range of piscivores than planktivores created a window for long periods at high latitudes. Latitudinal dependencies were essentially lost during the equinox, indicating a progressive compression of the window from early summer into autumn.
4. Model results show that diel‐seasonal foraging and predation risk in freshwater pelagic ecosystems changes considerably with latitude, turbidity and cloud cover. These changes alter the structure of pelagic predator‐prey interactions, and in turn, the broader role of pelagic consumers in habitat coupling in lakes.
This article is protected by copyright. All rights reserved.PubDate: 2014-09-29T10:57:11.417498-05:DOI: 10.1111/1365-2656.12295

Authors:E. Keith Bowers; Charles F. Thompson, Scott K. SakalukAbstract: A major component of sex‐allocation theory, the Trivers‐Willard Model (TWM), posits that sons and daughters are differentially affected by variation in the rearing environment. In many species, the amount of parental care received is expected to have differing effects on the fitness of males and females. When this occurs, the TWM predicts that selection should favour adjustment of the offspring sex ratio in relation to the expected fitness return from offspring. However, evidence for sex‐by‐environment effects is mixed and little is known about the adaptive significance of producing either sex.
Here, we test whether offspring sex ratios vary according to predictions of the TWM in the house wren (Troglodytes aedon, Vieillot). We also test the assumption of a sex‐by‐environment effect on offspring using two experiments, one in which we manipulated age‐differences among nestlings within broods, and another in which we held nestling age constant but manipulated brood size.
As predicted, females with high investment ability over‐produced sons relative to those with lower ability. Males were also over‐produced early within breeding seasons. In our experiments, the body mass of sons was more strongly affected by the sibling‐competitive environment and resource availability than that of daughters: males grew heavier than females when reared in good conditions but were lighter than females when in poor conditions.
Parents rearing broods with 1:1 sex ratios were more productive than parents rearing broods biased more strongly towards sons or daughters, suggesting that selection favours the production of mixed‐sex broods. However, differences in the condition of offspring as neonates persisted to adulthood, and their reproductive success as adults varied with the body mass of sons, but not daughters, prior to independence from parental care. Thus, selection should favour slight but predictable variations in the sex ratio in relation to the quality of offspring that parents are able to produce.
Offspring sex interacts with the neonatal environment to influence offspring fitness, thus favouring sex‐ratio adjustment by parents. However, increased sensitivity of males to environmental conditions, such as sibling rivalry and resource availability, reduces the fitness returns from highly male‐biased broods.
This article is protected by copyright. All rights reserved.PubDate: 2014-09-29T10:56:56.394628-05:DOI: 10.1111/1365-2656.12294

Authors:Lotte Schlicht; Mihai Valcu, Bart KempenaersAbstract: Most studies on extra‐pair paternity (EPP) focus either on a specific male's extra‐pair gains or his extra‐pair losses. For an individual bird however, mate choice or mate availability may underlie strong spatial restrictions. Disregarding this spatial aspect may underestimate or mask effects of parameters influencing observed EPP patterns.
Here, we propose a spatially explicit model for investigating the probability of having extra‐pair offspring (EPO) within local networks of breeding pairs. The dataset includes all realized and unrealized potential extra‐pair matings. This method is biologically meaningful because it allows (a) considering both members of an extra‐pair mating as well as their social mates, and (b) direct modelling of the spatial context in which extra‐pair behaviour occurs. The method has the advantage that it can provide inference about the relative contribution of spatial and non‐spatial parameters, and about the relative importance of male and female neighbourhoods.
We apply this method to parentage data from 1025 broods collected over 12 breeding seasons in two independent study populations of blue tits (Cyanistes caeruleus). We investigate a set of predictions based on the EPP literature, namely that EPP depends on male age and body size, breeding density, and breeding synchrony. In all analyses, we control for breeding distance, a parameter that is expected to influence EPP even under random mating.
The results show that older and larger males were more likely to sire EPO, but both effects decreased with increasing breeding distance. Local breeding density but not synchrony predicted whether a particular male‐female combination had EPO, at least in one of the study areas. Apart from breeding distance, male age had the strongest effect on EPP, followed by a measure of breeding density. The method thus allows a comprehensive assessment of the relative importance of different types of spatial and non‐spatial parameters to explain variation in the occurrence of EPP, while controlling for the fact that individuals that breed further apart are less likely to have EPO.
The proposed approach is not limited to investigate EPP, but can be applied to other behavioural interactions between two individuals, such as dominance, competition, and (social) mating.
This article is protected by copyright. All rights reserved.PubDate: 2014-09-29T10:56:41.956803-05:DOI: 10.1111/1365-2656.12293

Authors:Rachel A. Paterson; Jaimie T. A. Dick, Daniel W. Pritchard, Marilyn Ennis, Melanie J. Hatcher, Alison M. DunnAbstract: Predatory functional responses play integral roles in predator‐prey dynamics, and their assessment promises greater understanding and prediction of the predatory impacts of invasive species.
Other inter‐specific interactions, however, such as parasitism and higher‐order predation, have the potential to modify predator‐prey interactions and thus the predictive capability of the comparative functional response approach.
We used a four‐species community module (higher‐order predator; focal native or invasive predators; parasites of focal predators; native prey) to compare the predatory functional responses of native Gammarus duebeni celticus and invasive Gammarus pulex amphipods towards three invertebrate prey species (Asellus aquaticus, Simulium spp., Baetis rhodani), thus quantifying the context dependencies of parasitism and a higher‐order fish predator on these functional responses.
Our functional response experiments demonstrated that the invasive amphipod had a higher predatory impact (lower handling time) on two of three prey species, which reflects patterns of impact observed in the field. The community module also revealed that parasitism had context dependent influences, for one prey species, with the potential to further reduce the predatory impact of the invasive amphipod or increase the predatory impact of the native amphipod in the presence of a higher‐order fish predator.
Partial consumption of prey was similar for both predators and occurred increasingly in the order A. aquaticus, Simulium spp., and B. rhodani. This was associated with increasing prey densities, but showed no context dependencies with parasitism or higher‐order fish predator.
This study supports the applicability of comparative functional responses as a tool to predict and assess invasive species impacts incorporating multiple context dependencies.
This article is protected by copyright. All rights reserved.PubDate: 2014-09-29T10:56:26.519042-05:DOI: 10.1111/1365-2656.12292

Authors:Inger M. Aalberg Haugen; Karl GotthardAbstract: 1.Seasonal phenotypic plasticity entails differential trait expression depending on the time of season. The facultative induction of winter diapause in temperate insects is a developmental switch mechanism often leading to differential expression in life‐history traits. However, when there is a latitudinal shift from a bivoltine to univoltine life‐cycle, selection for pathway‐specific expression is disrupted, which may allow drift towards less optimal trait values within the non‐selected pathway.
2.We use field‐ and experimental data from five Swedish populations of Pararge aegeria to investigate latitudinal variation in voltinism, local adaptation in the diapause switch, and footprints of selection on pathway‐specific regulation of life‐history traits and sexual dimorphism in larval development.
3.Field data clearly illustrated how natural populations gradually shift from bivoltinism to univoltinism as latitude increases. This was supported experimentally as the decrease in direct development at higher latitudes was accompanied by increasing critical daylengths, suggesting local adaptation in the diapause switch.
4.The differential expression among developmental pathways in development time and growth rate was significantly less pronounced in univoltine populations. Univoltine populations showed no significant signs of protandry during larval development, suggesting that erosion of the direct development pathway under relaxed selection has led to the loss of its sex‐specific modifications.
This article is protected by copyright. All rights reserved.PubDate: 2014-09-29T10:56:09.603057-05:DOI: 10.1111/1365-2656.12291

Authors:Madelon kerk; David P. Onorato, Marc A. Criffield, Benjamin M. Bolker, Ben C. Augustine, Scott A. Mckinley, Madan K. OliAbstract: Animals must move to find food and mates, and to avoid predators; movement thus influences survival and reproduction, and ultimately determines fitness. Precise description of movement and understanding of spatial and temporal patterns as well as relationships with intrinsic and extrinsic factors is important both for theoretical and applied reasons. We applied hidden semi‐Markov models (HSMM) to hourly geographic positioning system (GPS) location data to understand movement patterns of the endangered Florida panther (Puma concolor coryi) and to discern factors influencing these patterns. Three distinct movement modes were identified: (1) Resting mode, characterized by short step lengths and turning angles around 180o; (2) Moderately active (or intermediate) mode characterized by intermediate step lengths and variable turning angles, and (3) Traveling mode, characterized by long step lengths and turning angles around 0o. Males and females, and females with and without kittens, exhibited distinctly different movement patterns. Using the Viterbi algorithm, we show that differences in movement patterns of male and female Florida panthers were a consequence of sex‐specific differences in diurnal patterns of state occupancy and sex‐specific differences in state‐specific movement parameters, whereas the differences between females with and without dependent kittens were caused solely by variation in state occupancy. Our study demonstrates the use of HSMM methodology to precisely describe movement and to dissect differences in movement patterns according to sex, and reproductive status.
This article is protected by copyright. All rights reserved.PubDate: 2014-09-24T00:10:41.421186-05:DOI: 10.1111/1365-2656.12290

Authors:Ken Tan; Shihao Dong, Xiwen Liu, Weiweng Chen, Yuchong Wang, Benjamin P. Oldroyd, Tanya LattyAbstract: 1.Most models of animal choice behaviour assume that desirable but unavailable options, such as a high quality, but inhabited nest sites, do not influence an individual's preferences for the remaining options. However, experiments suggest that in mammals the mere presence of such ‘phantom’ alternatives can alter, and even reverse, an individual's preferences for other items in a choice set.
2.Phantom alternatives may be widespread in nature, as they occur whenever a resource is visible, but unavailable at the time of choice. They are particularly relevant for nectar‐foraging animals, where previously rewarding flowers may sometimes be empty. Here we investigate the effect of phantom alternatives on feeder preferences in the eastern honey bee, Apis cerana.
3.First, we tested the effects of unattractive and attractive phantom alternatives by presenting individual bees with either a binary choice set containing two feeders that differed strongly in two qualities, but were equally preferred overall (‘option 1’ and ‘option 2’), or a ternary choice set containing option 1, option 2 and one of two phantom types (unattractive and attractive). Second, we determined whether phantoms increase (similarity effect) or decrease (dissimilarity effect) preference for phantom‐similar choices.
4.In binary trials, bees had no significant preference for option 1 or option 2. However, after encountering an attractive phantom alternative, individual bees preferred option 2. The unattractive phantom did not influence bee preferences. Phantoms consistently changed individual bee preferences in favour of the phantom‐similar choice. This means that the presence of an attractive food source, even if it is unavailable, can influence preference relationships between remaining items in the choice set.
5.Our findings highlight the importance of considering the potential for phantom effects when studying the foraging behaviour of animals. Our results are particularly relevant for nectarivores, where empty, but previously rewarding flowers are a common occurrence. Since an increase in pollinator visits can result in higher seed set, our results open up the possibility that by shifting pollinator preferences, empty flowers could have otherwise‐unpredicted influences on community composition, plant‐pollinator interactions and pollinator behaviour.
This article is protected by copyright. All rights reserved.PubDate: 2014-09-22T11:39:17.153979-05:DOI: 10.1111/1365-2656.12288

Authors:Jani Heino; Janne AlahuhtaAbstract: 1. Regional faunas are structured by historical, spatial and environmental factors. We studied large‐scale variation in four ecologically different beetle groups (Coleoptera: Dytiscidae, Carabidae, Hydrophiloidea, Cerambycidae) along climate, land cover and geographical gradients, examined faunal breakpoints in relation to environmental variables, and investigated the best fit pattern of assemblage variation (i.e. randomness, checkerboards, nestedness, evenly‐spaced, Gleasonian, Clementsian). We applied statistical methods typically used in the analysis of local ecological communities to provide novel insights into faunal compositional patterns at large spatial grain and geographical extent.
2. We found that spatially‐structured variation in climate and land cover accounted for most variation in each beetle group in partial redundancy analyses, whereas the individual effect of each explanatory variable group was generally much less important in accounting for variation in provincial species composition.
3. We also found that climate variables were most strongly associated with faunal breakpoints, with temperature‐related variables alone accounting for about 20% of variation at the first node of multivariate regression tree for each beetle group. The existence of faunal breakpoints was also shown by the “elements of faunal structure” analyses, which suggested Clementsian gradients across the provinces, i.e., that there were two or more clear groups of species responding similarly to the underlying ecological gradients.
4. The four beetle groups showed highly similar biogeographical patterns across our study area. The fact that temperature was related to faunal breakpoints in the species composition of each beetle group suggests that climate sets a strong filter to the distributions of species at this combination of spatial grain and spatial extent. This finding held true despite the ecological differences among the four beetle groups, ranging from fully aquatic to fully terrestrial, and from herbivorous to predaceous species.
5. The existence of Clementsian gradients may be a common phenomenon at large scales, and it is likely to be caused by crossing multiple species pools determined by climatic and historical factors on the distributions of species.
This article is protected by copyright. All rights reserved.PubDate: 2014-09-22T11:39:02.032429-05:DOI: 10.1111/1365-2656.12287

Authors:Sebastián F. Sendoya; Paulo S. OliveiraAbstract: Ant foraging on foliage can substantially affect how phytophagous insects use host plants and represents a high predation risk for caterpillars, which are important folivores. Ant‐plant‐herbivore interactions are especially pervasive in cerrado savanna due to continuous ant visitation to liquid food sources on foliage (extrafloral nectaries, insect honeydew). While searching for liquid rewards on plants, aggressive ants frequently attack or kill insect herbivores, decreasing their numbers.
Because ants vary in diet and aggressiveness, their effect on herbivores also varies. Additionally, the differential occurrence of ant attractants (plant and insect exudates) on foliage produces variable levels of ant foraging within local floras and among localities. Here, we investigate how variation of ant communities and of traits among host plant species (presence or absence of ant attractants) can change the effect of carnivores (predatory ants) on herbivore communities (caterpillars) in a cerrado savanna landscape.
We sampled caterpillars and foliage‐foraging ants in four cerrado localities (70‐460 km apart). We found that: (i) caterpillar infestation was negatively related with ant visitation to plants; (ii) this relationship depended on local ant abundance and species composition, and on local preference by ants for plants with liquid attractants, and (iii) was not related to local plant richness or plant size; (iv) the relationship between presence of ant attractants and caterpillar abundance varied among sites from negative to neutral; and (v) caterpillars feeding on plants with ant attractants are more resistant to ant predation than those feeding on plants lacking attractants.
Liquid food on foliage mediates host plant quality for lepidopterans by promoting generalized ant‐caterpillar antagonism. Our study in cerrado shows that the negative effects of generalist predatory ants on herbivores are detectable at a community level, affecting patterns of abundance and host plant use by lepidopterans.
The magnitude of ant‐induced effects on caterpillar occurrence across the cerrado landscape may depend on how ants use plants locally and how they respond to liquid food on plants at different habitats. This study enhances the relevance of plant‐ant and ant‐herbivore interactions in cerrado, and highlights the importance of a tritrophic perspective in this ant‐rich environment.
This article is protected by copyright. All rights reserved.PubDate: 2014-09-22T11:38:51.493839-05:DOI: 10.1111/1365-2656.12286

Authors:Sarah C. Maunsell; Roger L. Kitching, Chris J. Burwell, Rebecca J. MorrisAbstract: Gradients in elevation are increasingly used to investigate how species respond to changes in local climatic conditions. While many studies have shown elevational patterns in species richness and turnover, little is known about how food web structure is affected by elevation.
Contrasting responses of predator and prey species to elevation may lead to changes in food web structure. We investigated how the quantitative structure of a herbivore‐parasitoid food web changes with elevation in Australian subtropical rainforest.
On four occasions, spread over one year, we hand‐collected leaf miners at twelve sites, along three elevational gradients (between 493 m and 1159 m a.s.l). A total of 5030 insects, including 603 parasitoids were reared, and summary food webs were created for each site. We also carried out a replicated manipulative experiment by translocating an abundant leaf‐mining weevil, Platynotocis sp., which largely escaped parasitism at high elevations (≥900m a.s.l.), to lower, warmer elevations, to test if it would experience higher parasitism pressure.
We found strong evidence that the environmental change that occurs with increasing elevation affects food web structure. Quantitative measures of generality, vulnerability and interaction evenness decreased significantly with increasing elevation (and decreasing temperature), whilst elevation did not have a significant effect on connectance. Mined plant composition also had a significant effect on generality and vulnerability, but not on interaction evenness. Several relatively abundant species of leaf miner appeared to escape parasitism at higher elevations, but contrary to our prediction, Platynotocis sp. did not experience greater levels of parasitism when translocated to lower elevations.
Our study indicates that leaf‐mining herbivores and their parasitoids respond differently to environmental conditions imposed by elevation, thus producing structural changes in their food webs. Increasing temperatures and changes in vegetation communities that are likely to result from climate change may have a restructuring effect on host‐parasitoid food webs. Our translocation experiment, however, indicated that leaf miners currently escaping parasitism at high elevations may not automatically experience higher parasitism under warmer conditions and future changes in food web structure may depend on the ability of parasitoids to adapt to novel hosts.
This article is protected by copyright. All rights reserved.PubDate: 2014-09-22T02:56:07.595024-05:DOI: 10.1111/1365-2656.12285

Authors:Hawthorne L. Beyer; Eliezer Gurarie, Luca Börger, Manuela Panzacchi, Mathieu Basille, Ivar Herfindal, Bram Van Moorter, Subhash R. Lele, Jason MatthiopoulosAbstract: 1. Impediments to animal movement are ubiquitous and vary widely in both scale and permeability. It is essential to understand how impediments alter ecological dynamics via their influence on animal behavioural strategies governing space use and, for anthropogenic features such as roads and fences, how to mitigate these effects to effectively manage species and landscapes.
2. Here, we focused primarily on barriers to movement, which we define as features that cannot be circumnavigated but may be crossed. Responses to barriers will be influenced by the movement capabilities of the animal, its proximity to the barriers, and habitat preference. We developed a mechanistic modelling framework for simultaneously quantifying the permeability and proximity effects of barriers on habitat preference and movement.
3. We used simulations based on our model to demonstrate how parameters on movement, habitat preference and barrier permeability can be estimated statistically. We then applied the model to a case study of road effects on wild mountain reindeer summer movements.
4. This framework provided unbiased and precise parameter estimates across a range of strengths of preferences and barrier permeabilities. The quality of permeability estimates, however, was correlated with the number of times the barrier is crossed and the number of locations in proximity to barriers. In the case study we found reindeer avoided areas near roads and that roads are semi‐permeable barriers to movement. There was strong avoidance of roads extending up to approximately 1 km for four of five animals, and having to cross roads reduced the probability of movement by 68.6% (range 3.5‐99.5%).
5. Human infrastructure has embedded within it the idea of networks: nodes connected by linear features such as roads, rail tracks, pipelines, fences and cables, many of which divide the landscape and limit animal movement. The unintended but potentially profound consequences of infrastructure on animals remain poorly understood. The rigorous framework for simultaneously quantifying movement, habitat preference and barrier permeability developed here begins to address this knowledge gap.
This article is protected by copyright. All rights reserved.PubDate: 2014-08-25T02:18:19.581003-05:DOI: 10.1111/1365-2656.12275

Abstract: Movement patterns offer a rich source of information on animal behavior and the ecological significance of landscape attributes. This is especially useful for species occupying remote landscapes where direct behavioral observations are limited. In this study we fit a mechanistic model of animal cognition and movement to GPS positional data of woodland caribou (Rangifer tarandus caribou; Gmelin 1788) collected over a wide range of ecological conditions.
The model explicitly tracks individual animal informational state over space and time, with resulting parameter estimates that have direct cognitive and ecological meaning. Three biotic landscape attributes were hypothesized to motivate caribou movement: forage abundance (dietary digestible biomass), wolf (Canis lupus; Linnaeus, 1758) density, and moose (Alces alces; Linnaeus, 1758) habitat. Wolves are the main predator of caribou in this system and moose are their primary prey.
Resulting parameter estimates clearly indicated that forage abundance is an important driver of caribou movement patterns, with predator and moose avoidance often having a strong effect, but not for all individuals. From the cognitive perspective, our results support the notion that caribou rely on limited sensory inputs from their surroundings, as well as on long‐term spatial memory, to make informed movement decisions. Our study demonstrates how sensory, memory and motion capacities may interact with ecological fitness covariates to influence movement decisions by free‐ranging animals.
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Abstract: Habitats have substantial influence on the distribution and abundance of animals. Animals’ selective movement yields their habitat use. Animals generally are more abundant in habitats that are selected most strongly.
Models of habitat selection can be used to distribute animals on the landscape or their distribution can be modeled based on data of habitat use, occupancy, intensity of use, or counts of animals. When the population is at carrying capacity or in an ideal free distribution, habitat selection and related metrics of habitat use can be used to estimate abundance.
If the population is not at equilibrium, models have the flexibility to incorporate density into models of habitat selection; but abundance might be influenced by factors influencing fitness that are not directly related to habitat thereby compromising the use of habitat‐based models for predicting population size.
Scale and domain of the sampling frame, both in time and space, are crucial considerations limiting application of these models. Ultimately, identifying reliable models for predicting abundance from habitat data requires an understanding of the mechanisms underlying population regulation and limitation.
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Abstract: Several tetrapod lineages that have evolved to exploit marine environments (e.g., seals, seabirds, sea kraits) continue to rely upon land for reproduction; and thus, form dense colonies on suitable islands.
In birds and mammals (endotherms) the offspring cannot survive without their parents. Terrestrial colonies contain all age classes. In reptiles (ectotherms) this constraint is relaxed, because offspring are independent from birth. Hence, each age class has the potential to select sites with characteristics that favour them.
Our studies of sea snakes (sea kraits) in the lagoon of New Caledonia reveal marked spatial heterogeneity in age structure among colonies.
Sea krait colonies exhibit the endothermic “seal‐seabird” pattern (mixed age classes within populations) only where the lagoon is narrow. Where the lagoon is wide, most snake colonies are comprised primarily of a single age cohort. Nurseries are located near the coast, adult colonies offshore, and mixed colonies in between.
We suggest that ectothermy allows individuals to utilize habitats that are best‐suited to their own ecological requirements, a flexibility not available to endothermic marine taxa with obligate parental care.
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Abstract: 1.Chronic infections may have negative impacts on wildlife populations, yet their effects are difficult to detect in the absence of long‐term population monitoring. Brucella abortus, the bacteria responsible for bovine brucellosis, causes chronic infections and abortions in wild and domestic ungulates, but its impact on population dynamics is not well understood.
2.We report infection patterns and fitness correlates of bovine brucellosis in African buffalo based on (1) seven years of cross‐sectional disease surveys and (2) a four‐year longitudinal study in Kruger National Park (KNP), South Africa. We then used a matrix population model to translate these observed patterns into predicted population‐level effects.
3.Annual brucellosis seroprevalence ranged from 8.7% (95% CI=1.8‐15.6) to 47.6% (95% CI=35.1‐60.1), increased with age until adulthood (>6), and varied by location within KNP. Animals were on average in worse condition after testing positive for brucellosis (F=‐5.074, p

Abstract: Adult root vole, Microtus oeconomus. Photo credit: Alice Kenney.
Bian, J.‐H., Du, S.‐Y., Wu, Y., Cao, Y.‐F., Nie, X.‐H., He, H. & You, Z.‐B. (2015) Maternal effects and population regulation: maternal density‐induced reproduction suppression impairs offspring capacity in response to immediate environment in root voles Microtus oeconomus. Journal of Animal Ecology, 84, 326–336.
Ecologists, evolutionary biologists and biomedical researchers are investing great effort in understanding the impact maternal stress may have on offspring phenotypes. Bian et al. advance this field by providing evidence that density‐induced maternal stress programs offspring phenotypes, resulting in direct consequences on their fitness and population dynamics, but doing so in a context‐dependent manner. They suggest that intrinsic state alterations induced by maternal stress may be one ecological factor generating delayed density‐dependent effects. This research highlights the connection between maternal stress and population dynamics, and the importance of understanding the adaptive potential of such effects in a context‐dependent manner.
This article focuses on the study by Bian et al. (2015) and in doing so discusses how maternal stress programmes offspring phenotypes with direct consequences for population dynamics. It also provides an integrative life‐history framework necessary to fully understand the impact of maternal stress exposure.

Abstract: 1.Decades of theory and recent empirical results have shown that evolutionary, population, community and ecosystem properties are the result of feedbacks between ecological and evolutionary processes. The vast majority of theory and empirical research on these eco‐evolutionary feedbacks has focused on interactions among population size and mean traits of populations.
2.However, numbers and mean traits represent only a fraction of the possible feedback dimensions. Populations of many organisms consist of different size classes that differ in their impact on the environment and each other. Moreover, rarely do we know the map of ecological pathways through which changes in numbers or size structure cause evolutionary change. The goal of this study was to test the role of size structure in eco‐evolutionary feedbacks of Trinidadian guppies and to begin to build an eco‐evolutionary map along this unexplored dimension.
3.We used a factorial experiment in mesocosms wherein we crossed high and low predation guppy phenotypes with population size structure. We tested the ability of changes in size structure to generate selection on the demographic rates of guppies using an integral projection model (IPM). To understand how fitness differences among high and low predation phenotypes may be generated, we measured the response of the biomass of lower trophic levels and nutrient cycling to the different phenotype and size structure treatments.
4.We found a significant interaction between guppy phenotype and the size structure treatments for absolute fitness. Size structure had a very large effect on invertebrate biomass in the mesocosms, but there was little or no effect of the phenotype. The effect of size structure on algal biomass depended on guppy phenotype, with no difference in algal biomass in populations with more, smaller guppies, but a large decrease in algal biomass in mesocosms with phenotypes adapted to low predation risk.
5.These results indicate an important role for size structure partially driving eco‐evolutionary feedbacks in guppies. The changes in the ecosystem suggest that the absence of a steep decline in guppy fitness of the low predation risk populations is likely due to higher consumption of algae when invertebrates are comparatively rare. Overall, these results demonstrate size structure as a possible dimension through which eco‐evolutionary feedbacks may occur in natural populations.
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Abstract: 1.Host‐parasite interactions have the potential to influence broad scale ecological and evolutionary processes, levels of endemism, divergence patterns and distributions in host populations. Understanding the mechanisms involved requires identification of the factors that shape parasite distribution and prevalence.
2.A lack of comparative information on community‐level host‐parasite associations limits our understanding of the role of parasites in host population divergence processes. Avian malaria (haemosporodian) parasites in bird communities offer a tractable model system to examine the potential for pathogens to influence evolutionary processes in natural host populations.
3.Using cytochrome b variation, we characterized phylogenetic diversity and prevalence of two genera of avian haemosporidian parasites, Plasmodium and Haemoproteus, and analysed biogeographic patterns of lineages across islands and avian hosts, in southern Melanesian bird communities to identify factors that explain patterns of infection.
4.Plasmodium spp. displayed isolation by distance effects, a significant amount of genetic variation distributed among islands but insignificant amounts among host species and families, and strong local island effects with respect to prevalence. Haemoproteus spp. did not display isolation by distance patterns, showed significant structuring of genetic variation among avian host species and families, and significant host species prevalence patterns.
5.These differences suggest that Plasmodium spp. infection patterns were shaped by geography and the abiotic environment, whereas Haemoproteus spp. infection patterns were shaped predominantly by host associations. Heterogeneity in the complement and prevalence of parasite lineages infecting local bird communities likely exposes host species to a mosaic of spatially divergent disease selection pressures across their naturally fragmented distributions in southern Melanesia. Host associations for Haemoproteus spp. indicate a capacity for the formation of locally co‐adapted host‐parasite relationships, a feature that may limit intraspecific gene flow or range expansions of closely related host species.
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